| Message ID | 1358341895-4369-1-git-send-email-jacob.jun.pan@linux.intel.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Zhang Rui |
| Headers | show |
On Wed, 2013-01-16 at 05:11 -0800, Jacob Pan wrote: > Intel PowerClamp driver performs synchronized idle injection across > all online CPUs. The goal is to maintain a given package level C-state > ratio. > > Compared to other throttling methods already exist in the kernel, > such as ACPI PAD (taking CPUs offline) and clock modulation, this is often > more efficient in terms of performance per watt. > > Please refer to Documentation/thermal/intel_powerclamp.txt for more details. > > Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> Reviewed-by: Zhang Rui <rui.zhang@intel.com> Rafael, can you take this please? I'm not going to push anything except bug fixes until next merge window. thanks, rui > --- > Documentation/thermal/intel_powerclamp.txt | 307 +++++++++++ > drivers/thermal/Kconfig | 10 + > drivers/thermal/Makefile | 2 + > drivers/thermal/intel_powerclamp.c | 788 ++++++++++++++++++++++++++++ > 4 files changed, 1107 insertions(+) > create mode 100644 Documentation/thermal/intel_powerclamp.txt > create mode 100644 drivers/thermal/intel_powerclamp.c > > diff --git a/Documentation/thermal/intel_powerclamp.txt b/Documentation/thermal/intel_powerclamp.txt > new file mode 100644 > index 0000000..332de4a > --- /dev/null > +++ b/Documentation/thermal/intel_powerclamp.txt > @@ -0,0 +1,307 @@ > + ======================= > + INTEL POWERCLAMP DRIVER > + ======================= > +By: Arjan van de Ven <arjan@linux.intel.com> > + Jacob Pan <jacob.jun.pan@linux.intel.com> > + > +Contents: > + (*) Introduction > + - Goals and Objectives > + > + (*) Theory of Operation > + - Idle Injection > + - Calibration > + > + (*) Performance Analysis > + - Effectiveness and Limitations > + - Power vs Performance > + - Scalability > + - Calibration > + - Comparison with Alternative Techniques > + > + (*) Usage and Interfaces > + - Generic Thermal Layer (sysfs) > + - Kernel APIs (TBD) > + > +============ > +INTRODUCTION > +============ > + > +Consider the situation where a system’s power consumption must be > +reduced at runtime, due to power budget, thermal constraint, or noise > +level, and where active cooling is not preferred. Software managed > +passive power reduction must be performed to prevent the hardware > +actions that are designed for catastrophic scenarios. > + > +Currently, P-states, T-states (clock modulation), and CPU offlining > +are used for CPU throttling. > + > +On Intel CPUs, C-states provide effective power reduction, but so far > +they’re only used opportunistically, based on workload. With the > +development of intel_powerclamp driver, the method of synchronizing > +idle injection across all online CPU threads was introduced. The goal > +is to achieve forced and controllable C-state residency. > + > +Test/Analysis has been made in the areas of power, performance, > +scalability, and user experience. In many cases, clear advantage is > +shown over taking the CPU offline or modulating the CPU clock. > + > + > +=================== > +THEORY OF OPERATION > +=================== > + > +Idle Injection > +-------------- > + > +On modern Intel processors (Nehalem or later), package level C-state > +residency is available in MSRs, thus also available to the kernel. > + > +These MSRs are: > + #define MSR_PKG_C2_RESIDENCY 0x60D > + #define MSR_PKG_C3_RESIDENCY 0x3F8 > + #define MSR_PKG_C6_RESIDENCY 0x3F9 > + #define MSR_PKG_C7_RESIDENCY 0x3FA > + > +If the kernel can also inject idle time to the system, then a > +closed-loop control system can be established that manages package > +level C-state. The intel_powerclamp driver is conceived as such a > +control system, where the target set point is a user-selected idle > +ratio (based on power reduction), and the error is the difference > +between the actual package level C-state residency ratio and the target idle > +ratio. > + > +Injection is controlled by high priority kernel threads, spawned for > +each online CPU. > + > +These kernel threads, with SCHED_FIFO class, are created to perform > +clamping actions of controlled duty ratio and duration. Each per-CPU > +thread synchronizes its idle time and duration, based on the rounding > +of jiffies, so accumulated errors can be prevented to avoid a jittery > +effect. Threads are also bound to the CPU such that they cannot be > +migrated, unless the CPU is taken offline. In this case, threads > +belong to the offlined CPUs will be terminated immediately. > + > +Running as SCHED_FIFO and relatively high priority, also allows such > +scheme to work for both preemptable and non-preemptable kernels. > +Alignment of idle time around jiffies ensures scalability for HZ > +values. This effect can be better visualized using a Perf timechart. > +The following diagram shows the behavior of kernel thread > +kidle_inject/cpu. During idle injection, it runs monitor/mwait idle > +for a given "duration", then relinquishes the CPU to other tasks, > +until the next time interval. > + > +The NOHZ schedule tick is disabled during idle time, but interrupts > +are not masked. Tests show that the extra wakeups from scheduler tick > +have a dramatic impact on the effectiveness of the powerclamp driver > +on large scale systems (Westmere system with 80 processors). > + > +CPU0 > + ____________ ____________ > +kidle_inject/0 | sleep | mwait | sleep | > + _________| |________| |_______ > + duration > +CPU1 > + ____________ ____________ > +kidle_inject/1 | sleep | mwait | sleep | > + _________| |________| |_______ > + ^ > + | > + | > + roundup(jiffies, interval) > + > +Only one CPU is allowed to collect statistics and update global > +control parameters. This CPU is referred to as the controlling CPU in > +this document. The controlling CPU is elected at runtime, with a > +policy that favors BSP, taking into account the possibility of a CPU > +hot-plug. > + > +In terms of dynamics of the idle control system, package level idle > +time is considered largely as a non-causal system where its behavior > +cannot be based on the past or current input. Therefore, the > +intel_powerclamp driver attempts to enforce the desired idle time > +instantly as given input (target idle ratio). After injection, > +powerclamp moniors the actual idle for a given time window and adjust > +the next injection accordingly to avoid over/under correction. > + > +When used in a causal control system, such as a temperature control, > +it is up to the user of this driver to implement algorithms where > +past samples and outputs are included in the feedback. For example, a > +PID-based thermal controller can use the powerclamp driver to > +maintain a desired target temperature, based on integral and > +derivative gains of the past samples. > + > + > + > +Calibration > +----------- > +During scalability testing, it is observed that synchronized actions > +among CPUs become challenging as the number of cores grows. This is > +also true for the ability of a system to enter package level C-states. > + > +To make sure the intel_powerclamp driver scales well, online > +calibration is implemented. The goals for doing such a calibration > +are: > + > +a) determine the effective range of idle injection ratio > +b) determine the amount of compensation needed at each target ratio > + > +Compensation to each target ratio consists of two parts: > + > + a) steady state error compensation > + This is to offset the error occurring when the system can > + enter idle without extra wakeups (such as external interrupts). > + > + b) dynamic error compensation > + When an excessive amount of wakeups occurs during idle, an > + additional idle ratio can be added to quiet interrupts, by > + slowing down CPU activities. > + > +A debugfs file is provided for the user to examine compensation > +progress and results, such as on a Westmere system. > +[jacob@nex01 ~]$ cat > +/sys/kernel/debug/intel_powerclamp/powerclamp_calib > +controlling cpu: 0 > +pct confidence steady dynamic (compensation) > +0 0 0 0 > +1 1 0 0 > +2 1 1 0 > +3 3 1 0 > +4 3 1 0 > +5 3 1 0 > +6 3 1 0 > +7 3 1 0 > +8 3 1 0 > +... > +30 3 2 0 > +31 3 2 0 > +32 3 1 0 > +33 3 2 0 > +34 3 1 0 > +35 3 2 0 > +36 3 1 0 > +37 3 2 0 > +38 3 1 0 > +39 3 2 0 > +40 3 3 0 > +41 3 1 0 > +42 3 2 0 > +43 3 1 0 > +44 3 1 0 > +45 3 2 0 > +46 3 3 0 > +47 3 0 0 > +48 3 2 0 > +49 3 3 0 > + > +Calibration occurs during runtime. No offline method is available. > +Steady state compensation is used only when confidence levels of all > +adjacent ratios have reached satisfactory level. A confidence level > +is accumulated based on clean data collected at runtime. Data > +collected during a period without extra interrupts is considered > +clean. > + > +To compensate for excessive amounts of wakeup during idle, additional > +idle time is injected when such a condition is detected. Currently, > +we have a simple algorithm to double the injection ratio. A possible > +enhancement might be to throttle the offending IRQ, such as delaying > +EOI for level triggered interrupts. But it is a challenge to be > +non-intrusive to the scheduler or the IRQ core code. > + > + > +CPU Online/Offline > +------------------ > +Per-CPU kernel threads are started/stopped upon receiving > +notifications of CPU hotplug activities. The intel_powerclamp driver > +keeps track of clamping kernel threads, even after they are migrated > +to other CPUs, after a CPU offline event. > + > + > +===================== > +Performance Analysis > +===================== > +This section describes the general performance data collected on > +multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P). > + > +Effectiveness and Limitations > +----------------------------- > +The maximum range that idle injection is allowed is capped at 50 > +percent. As mentioned earlier, since interrupts are allowed during > +forced idle time, excessive interrupts could result in less > +effectiveness. The extreme case would be doing a ping -f to generated > +flooded network interrupts without much CPU acknowledgement. In this > +case, little can be done from the idle injection threads. In most > +normal cases, such as scp a large file, applications can be throttled > +by the powerclamp driver, since slowing down the CPU also slows down > +network protocol processing, which in turn reduces interrupts. > + > +When control parameters change at runtime by the controlling CPU, it > +may take an additional period for the rest of the CPUs to catch up > +with the changes. During this time, idle injection is out of sync, > +thus not able to enter package C- states at the expected ratio. But > +this effect is minor, in that in most cases change to the target > +ratio is updated much less frequently than the idle injection > +frequency. > + > +Scalability > +----------- > +Tests also show a minor, but measurable, difference between the 4P/8P > +Ivy Bridge system and the 80P Westmere server under 50% idle ratio. > +More compensation is needed on Westmere for the same amount of > +target idle ratio. The compensation also increases as the idle ratio > +gets larger. The above reason constitutes the need for the > +calibration code. > + > +On the IVB 8P system, compared to an offline CPU, powerclamp can > +achieve up to 40% better performance per watt. (measured by a spin > +counter summed over per CPU counting threads spawned for all running > +CPUs). > + > +==================== > +Usage and Interfaces > +==================== > +The powerclamp driver is registered to the generic thermal layer as a > +cooling device. Currently, it’s not bound to any thermal zones. > + > +jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . * > +cur_state:0 > +max_state:50 > +type:intel_powerclamp > + > +Example usage: > +- To inject 25% idle time > +$ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state > +" > + > +If the system is not busy and has more than 25% idle time already, > +then the powerclamp driver will not start idle injection. Using Top > +will not show idle injection kernel threads. > + > +If the system is busy (spin test below) and has less than 25% natural > +idle time, powerclamp kernel threads will do idle injection, which > +appear running to the scheduler. But the overall system idle is still > +reflected. In this example, 24.1% idle is shown. This helps the > +system admin or user determine the cause of slowdown, when a > +powerclamp driver is in action. > + > + > +Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie > +Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st > +Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers > +Swap: 4087804k total, 0k used, 4087804k free, 945336k cached > + > + PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > + 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin > + 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0 > + 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3 > + 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1 > + 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2 > + 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox > + 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg > + 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz > + > +Tests have shown that by using the powerclamp driver as a cooling > +device, a PID based userspace thermal controller can manage to > +control CPU temperature effectively, when no other thermal influence > +is added. For example, a UltraBook user can compile the kernel under > +certain temperature (below most active trip points). > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig > index c2c77d1..7d90ab8 100644 > --- a/drivers/thermal/Kconfig > +++ b/drivers/thermal/Kconfig > @@ -122,4 +122,14 @@ config DB8500_CPUFREQ_COOLING > bound cpufreq cooling device turns active to set CPU frequency low to > cool down the CPU. > > +config INTEL_POWERCLAMP > + tristate "Intel PowerClamp idle injection driver" > + depends on THERMAL > + depends on X86 > + depends on CPU_SUP_INTEL > + help > + Enable this to enable Intel PowerClamp idle injection driver. This > + enforce idle time which results in more package C-state residency. The > + user interface is exposed via generic thermal framework. > + > endif > diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile > index d8da683..574f5f5 100644 > --- a/drivers/thermal/Makefile > +++ b/drivers/thermal/Makefile > @@ -18,3 +18,5 @@ obj-$(CONFIG_RCAR_THERMAL) += rcar_thermal.o > obj-$(CONFIG_EXYNOS_THERMAL) += exynos_thermal.o > obj-$(CONFIG_DB8500_THERMAL) += db8500_thermal.o > obj-$(CONFIG_DB8500_CPUFREQ_COOLING) += db8500_cpufreq_cooling.o > +obj-$(CONFIG_INTEL_POWERCLAMP) += intel_powerclamp.o > + > diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c > new file mode 100644 > index 0000000..81ebf87 > --- /dev/null > +++ b/drivers/thermal/intel_powerclamp.c > @@ -0,0 +1,788 @@ > +/* > + * intel_powerclamp.c - package c-state idle injection > + * > + * Copyright (c) 2012, Intel Corporation. > + * > + * Authors: > + * Arjan van de Ven <arjan@linux.intel.com> > + * Jacob Pan <jacob.jun.pan@linux.intel.com> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms and conditions of the GNU General Public License, > + * version 2, as published by the Free Software Foundation. > + * > + * This program is distributed in the hope it will be useful, but WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + * > + * You should have received a copy of the GNU General Public License along with > + * this program; if not, write to the Free Software Foundation, Inc., > + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. > + * > + * > + * TODO: > + * 1. better handle wakeup from external interrupts, currently a fixed > + * compensation is added to clamping duration when excessive amount > + * of wakeups are observed during idle time. the reason is that in > + * case of external interrupts without need for ack, clamping down > + * cpu in non-irq context does not reduce irq. for majority of the > + * cases, clamping down cpu does help reduce irq as well, we should > + * be able to differenciate the two cases and give a quantitative > + * solution for the irqs that we can control. perhaps based on > + * get_cpu_iowait_time_us() > + * > + * 2. synchronization with other hw blocks > + * > + * > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/module.h> > +#include <linux/kernel.h> > +#include <linux/delay.h> > +#include <linux/kthread.h> > +#include <linux/freezer.h> > +#include <linux/cpu.h> > +#include <linux/thermal.h> > +#include <linux/slab.h> > +#include <linux/tick.h> > +#include <linux/debugfs.h> > +#include <linux/seq_file.h> > + > +#include <asm/nmi.h> > +#include <asm/msr.h> > +#include <asm/mwait.h> > +#include <asm/cpu_device_id.h> > +#include <asm/idle.h> > +#include <asm/hardirq.h> > + > +#define MAX_TARGET_RATIO (50U) > +/* For each undisturbed clamping period (no extra wake ups during idle time), > + * we increment the confidence counter for the given target ratio. > + * CONFIDENCE_OK defines the level where runtime calibration results are > + * valid. > + */ > +#define CONFIDENCE_OK (3) > +/* Default idle injection duration, driver adjust sleep time to meet target > + * idle ratio. Similar to frequency modulation. > + */ > +#define DEFAULT_DURATION_JIFFIES (6) > + > +static unsigned int target_mwait; > +static struct dentry *debug_dir; > + > +/* user selected target */ > +static unsigned int set_target_ratio; > +static unsigned int current_ratio; > +static bool should_skip; > +static bool reduce_irq; > +static atomic_t idle_wakeup_counter; > +static unsigned int control_cpu; /* The cpu assigned to collect stat and update > + * control parameters. default to BSP but BSP > + * can be offlined. > + */ > +static bool clamping; > + > + > +static struct task_struct __percpu **powerclamp_thread; > +static struct thermal_cooling_device *cooling_dev; > +static unsigned long *cpu_clamping_mask; /* bit map for tracking per cpu > + * clamping thread > + */ > + > +static unsigned int duration; > +static unsigned int pkg_cstate_ratio_cur; > +static unsigned int window_size; > + > +static int duration_set(const char *arg, const struct kernel_param *kp) > +{ > + int ret = 0; > + unsigned long new_duration; > + > + ret = kstrtoul(arg, 10, &new_duration); > + if (ret) > + goto exit; > + if (new_duration > 25 || new_duration < 6) { > + pr_err("Out of recommended range %lu, between 6-25ms\n", > + new_duration); > + ret = -EINVAL; > + } > + > + duration = clamp(new_duration, 6ul, 25ul); > + smp_mb(); > + > +exit: > + > + return ret; > +} > + > +static struct kernel_param_ops duration_ops = { > + .set = duration_set, > + .get = param_get_int, > +}; > + > + > +module_param_cb(duration, &duration_ops, &duration, 0644); > +MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec."); > + > +struct powerclamp_calibration_data { > + unsigned long confidence; /* used for calibration, basically a counter > + * gets incremented each time a clamping > + * period is completed without extra wakeups > + * once that counter is reached given level, > + * compensation is deemed usable. > + */ > + unsigned long steady_comp; /* steady state compensation used when > + * no extra wakeups occurred. > + */ > + unsigned long dynamic_comp; /* compensate excessive wakeup from idle > + * mostly from external interrupts. > + */ > +}; > + > +static struct powerclamp_calibration_data cal_data[MAX_TARGET_RATIO]; > + > +static int window_size_set(const char *arg, const struct kernel_param *kp) > +{ > + int ret = 0; > + unsigned long new_window_size; > + > + ret = kstrtoul(arg, 10, &new_window_size); > + if (ret) > + goto exit_win; > + if (new_window_size > 10 || new_window_size < 2) { > + pr_err("Out of recommended window size %lu, between 2-10\n", > + new_window_size); > + ret = -EINVAL; > + } > + > + window_size = clamp(new_window_size, 2ul, 10ul); > + smp_mb(); > + > +exit_win: > + > + return ret; > +} > + > +static struct kernel_param_ops window_size_ops = { > + .set = window_size_set, > + .get = param_get_int, > +}; > + > +module_param_cb(window_size, &window_size_ops, &window_size, 0644); > +MODULE_PARM_DESC(window_size, "sliding window in number of clamping cycles\n" > + "\tpowerclamp controls idle ratio within this window. larger\n" > + "\twindow size results in slower response time but more smooth\n" > + "\tclamping results. default to 2."); > + > +static void find_target_mwait(void) > +{ > + unsigned int eax, ebx, ecx, edx; > + unsigned int highest_cstate = 0; > + unsigned int highest_subcstate = 0; > + int i; > + > + if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) > + return; > + > + cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); > + > + if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || > + !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) > + return; > + > + edx >>= MWAIT_SUBSTATE_SIZE; > + for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { > + if (edx & MWAIT_SUBSTATE_MASK) { > + highest_cstate = i; > + highest_subcstate = edx & MWAIT_SUBSTATE_MASK; > + } > + } > + target_mwait = (highest_cstate << MWAIT_SUBSTATE_SIZE) | > + (highest_subcstate - 1); > + > +} > + > +static u64 pkg_state_counter(void) > +{ > + u64 val; > + u64 count = 0; > + > + static bool skip_c2; > + static bool skip_c3; > + static bool skip_c6; > + static bool skip_c7; > + > + if (!skip_c2) { > + if (!rdmsrl_safe(MSR_PKG_C2_RESIDENCY, &val)) > + count += val; > + else > + skip_c2 = true; > + } > + > + if (!skip_c3) { > + if (!rdmsrl_safe(MSR_PKG_C3_RESIDENCY, &val)) > + count += val; > + else > + skip_c3 = true; > + } > + > + if (!skip_c6) { > + if (!rdmsrl_safe(MSR_PKG_C6_RESIDENCY, &val)) > + count += val; > + else > + skip_c6 = true; > + } > + > + if (!skip_c7) { > + if (!rdmsrl_safe(MSR_PKG_C7_RESIDENCY, &val)) > + count += val; > + else > + skip_c7 = true; > + } > + > + return count; > +} > + > +static void noop_timer(unsigned long foo) > +{ > + /* empty... just the fact that we get the interrupt wakes us up */ > +} > + > +static unsigned int get_compensation(int ratio) > +{ > + unsigned int comp = 0; > + > + /* we only use compensation if all adjacent ones are good */ > + if (ratio == 1 && > + cal_data[ratio].confidence >= CONFIDENCE_OK && > + cal_data[ratio + 1].confidence >= CONFIDENCE_OK && > + cal_data[ratio + 2].confidence >= CONFIDENCE_OK) { > + comp = (cal_data[ratio].steady_comp + > + cal_data[ratio + 1].steady_comp + > + cal_data[ratio + 2].steady_comp) / 3; > + } else if (ratio == MAX_TARGET_RATIO - 1 && > + cal_data[ratio].confidence >= CONFIDENCE_OK && > + cal_data[ratio - 1].confidence >= CONFIDENCE_OK && > + cal_data[ratio - 2].confidence >= CONFIDENCE_OK) { > + comp = (cal_data[ratio].steady_comp + > + cal_data[ratio - 1].steady_comp + > + cal_data[ratio - 2].steady_comp) / 3; > + } else if (cal_data[ratio].confidence >= CONFIDENCE_OK && > + cal_data[ratio - 1].confidence >= CONFIDENCE_OK && > + cal_data[ratio + 1].confidence >= CONFIDENCE_OK) { > + comp = (cal_data[ratio].steady_comp + > + cal_data[ratio - 1].steady_comp + > + cal_data[ratio + 1].steady_comp) / 3; > + } > + > + /* REVISIT: simple penalty of double idle injection */ > + if (reduce_irq) > + comp = ratio; > + /* do not exceed limit */ > + if (comp + ratio >= MAX_TARGET_RATIO) > + comp = MAX_TARGET_RATIO - ratio - 1; > + > + return comp; > +} > + > +static void adjust_compensation(int target_ratio, unsigned int win) > +{ > + int delta; > + struct powerclamp_calibration_data *d = &cal_data[target_ratio]; > + > + /* > + * adjust compensations if confidence level has not been reached or > + * there are too many wakeups during the last idle injection period, we > + * cannot trust the data for compensation. > + */ > + if (d->confidence >= CONFIDENCE_OK || > + atomic_read(&idle_wakeup_counter) > > + win * num_online_cpus()) > + return; > + > + delta = set_target_ratio - current_ratio; > + /* filter out bad data */ > + if (delta >= 0 && delta <= (1+target_ratio/10)) { > + if (d->steady_comp) > + d->steady_comp = > + roundup(delta+d->steady_comp, 2)/2; > + else > + d->steady_comp = delta; > + d->confidence++; > + } > +} > + > +static bool powerclamp_adjust_controls(unsigned int target_ratio, > + unsigned int guard, unsigned int win) > +{ > + static u64 msr_last, tsc_last; > + u64 msr_now, tsc_now; > + > + /* check result for the last window */ > + msr_now = pkg_state_counter(); > + rdtscll(tsc_now); > + > + /* calculate pkg cstate vs tsc ratio */ > + if (!msr_last || !tsc_last) > + current_ratio = 1; > + else if (tsc_now-tsc_last) > + current_ratio = 100*(msr_now-msr_last)/ > + (tsc_now-tsc_last); > + > + /* update record */ > + msr_last = msr_now; > + tsc_last = tsc_now; > + > + adjust_compensation(target_ratio, win); > + /* > + * too many external interrupts, set flag such > + * that we can take measure later. > + */ > + reduce_irq = atomic_read(&idle_wakeup_counter) >= > + 2 * win * num_online_cpus(); > + > + atomic_set(&idle_wakeup_counter, 0); > + /* if we are above target+guard, skip */ > + return set_target_ratio + guard <= current_ratio; > +} > + > +static int clamp_thread(void *arg) > +{ > + int cpunr = (unsigned long)arg; > + DEFINE_TIMER(wakeup_timer, noop_timer, 0, 0); > + static const struct sched_param param = { > + .sched_priority = MAX_USER_RT_PRIO/2, > + }; > + unsigned int count = 0; > + unsigned int target_ratio; > + > + set_bit(cpunr, cpu_clamping_mask); > + set_freezable(); > + init_timer_on_stack(&wakeup_timer); > + sched_setscheduler(current, SCHED_FIFO, ¶m); > + > + while (true == clamping && !kthread_should_stop() && > + cpu_online(cpunr)) { > + int sleeptime; > + unsigned long target_jiffies; > + unsigned int guard; > + unsigned int compensation = 0; > + int interval; /* jiffies to sleep for each attempt */ > + unsigned int duration_jiffies = msecs_to_jiffies(duration); > + unsigned int window_size_now; > + > + try_to_freeze(); > + /* > + * make sure user selected ratio does not take effect until > + * the next round. adjust target_ratio if user has changed > + * target such that we can converge quickly. > + */ > + target_ratio = set_target_ratio; > + guard = 1 + target_ratio/20; > + window_size_now = window_size; > + count++; > + > + /* > + * systems may have different ability to enter package level > + * c-states, thus we need to compensate the injected idle ratio > + * to achieve the actual target reported by the HW. > + */ > + compensation = get_compensation(target_ratio); > + interval = duration_jiffies*100/(target_ratio+compensation); > + > + /* align idle time */ > + target_jiffies = roundup(jiffies, interval); > + sleeptime = target_jiffies - jiffies; > + if (sleeptime <= 0) > + sleeptime = 1; > + schedule_timeout_interruptible(sleeptime); > + /* > + * only elected controlling cpu can collect stats and update > + * control parameters. > + */ > + if (cpunr == control_cpu && !(count%window_size_now)) { > + should_skip = > + powerclamp_adjust_controls(target_ratio, > + guard, window_size_now); > + smp_mb(); > + } > + > + if (should_skip) > + continue; > + > + target_jiffies = jiffies + duration_jiffies; > + mod_timer(&wakeup_timer, target_jiffies); > + if (unlikely(local_softirq_pending())) > + continue; > + /* > + * stop tick sched during idle time, interrupts are still > + * allowed. thus jiffies are updated properly. > + */ > + preempt_disable(); > + tick_nohz_idle_enter(); > + /* mwait until target jiffies is reached */ > + while (time_before(jiffies, target_jiffies)) { > + unsigned long ecx = 1; > + unsigned long eax = target_mwait; > + > + /* > + * REVISIT: may call enter_idle() to notify drivers who > + * can save power during cpu idle. same for exit_idle() > + */ > + local_touch_nmi(); > + stop_critical_timings(); > + __monitor((void *)¤t_thread_info()->flags, 0, 0); > + cpu_relax(); /* allow HT sibling to run */ > + __mwait(eax, ecx); > + start_critical_timings(); > + atomic_inc(&idle_wakeup_counter); > + } > + tick_nohz_idle_exit(); > + preempt_enable_no_resched(); > + } > + del_timer_sync(&wakeup_timer); > + clear_bit(cpunr, cpu_clamping_mask); > + > + return 0; > +} > + > +/* > + * 1 HZ polling while clamping is active, useful for userspace > + * to monitor actual idle ratio. > + */ > +static void poll_pkg_cstate(struct work_struct *dummy); > +static DECLARE_DELAYED_WORK(poll_pkg_cstate_work, poll_pkg_cstate); > +static void poll_pkg_cstate(struct work_struct *dummy) > +{ > + static u64 msr_last; > + static u64 tsc_last; > + static unsigned long jiffies_last; > + > + u64 msr_now; > + unsigned long jiffies_now; > + u64 tsc_now; > + > + msr_now = pkg_state_counter(); > + rdtscll(tsc_now); > + jiffies_now = jiffies; > + > + /* calculate pkg cstate vs tsc ratio */ > + if (!msr_last || !tsc_last) > + pkg_cstate_ratio_cur = 1; > + else { > + if (tsc_now - tsc_last) > + pkg_cstate_ratio_cur = 100 * (msr_now - msr_last)/ > + (tsc_now - tsc_last); > + } > + > + /* update record */ > + msr_last = msr_now; > + jiffies_last = jiffies_now; > + tsc_last = tsc_now; > + > + if (true == clamping) > + schedule_delayed_work(&poll_pkg_cstate_work, HZ); > +} > + > +static int start_power_clamp(void) > +{ > + unsigned long cpu; > + struct task_struct *thread; > + > + /* check if pkg cstate counter is completely 0, abort in this case */ > + if (!pkg_state_counter()) { > + pr_err("pkg cstate counter not functional, abort\n"); > + return -EINVAL; > + } > + > + set_target_ratio = clamp(set_target_ratio, 0U, MAX_TARGET_RATIO); > + /* prevent cpu hotplug */ > + get_online_cpus(); > + > + /* prefer BSP */ > + control_cpu = 0; > + if (!cpu_online(control_cpu)) > + control_cpu = smp_processor_id(); > + > + clamping = true; > + schedule_delayed_work(&poll_pkg_cstate_work, 0); > + > + /* start one thread per online cpu */ > + for_each_online_cpu(cpu) { > + struct task_struct **p = > + per_cpu_ptr(powerclamp_thread, cpu); > + > + thread = kthread_create_on_node(clamp_thread, > + (void *) cpu, > + cpu_to_node(cpu), > + "kidle_inject/%ld", cpu); > + /* bind to cpu here */ > + if (likely(!IS_ERR(thread))) { > + kthread_bind(thread, cpu); > + wake_up_process(thread); > + *p = thread; > + } > + > + } > + put_online_cpus(); > + > + return 0; > +} > + > +static void end_power_clamp(void) > +{ > + int i; > + struct task_struct *thread; > + > + clamping = false; > + /* > + * make clamping visible to other cpus and give per cpu clamping threads > + * sometime to exit, or gets killed later. > + */ > + smp_mb(); > + msleep(20); > + if (bitmap_weight(cpu_clamping_mask, num_possible_cpus())) { > + for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) { > + pr_debug("clamping thread for cpu %d alive, kill\n", i); > + thread = *per_cpu_ptr(powerclamp_thread, i); > + kthread_stop(thread); > + } > + } > +} > + > +static int powerclamp_cpu_callback(struct notifier_block *nfb, > + unsigned long action, void *hcpu) > +{ > + unsigned long cpu = (unsigned long)hcpu; > + struct task_struct *thread; > + struct task_struct **percpu_thread = > + per_cpu_ptr(powerclamp_thread, cpu); > + > + if (false == clamping) > + goto exit_ok; > + > + switch (action) { > + case CPU_ONLINE: > + thread = kthread_create_on_node(clamp_thread, > + (void *) cpu, > + cpu_to_node(cpu), > + "kidle_inject/%lu", cpu); > + if (likely(!IS_ERR(thread))) { > + kthread_bind(thread, cpu); > + wake_up_process(thread); > + *percpu_thread = thread; > + } > + /* prefer BSP as controlling CPU */ > + if (cpu == 0) { > + control_cpu = 0; > + smp_mb(); > + } > + break; > + case CPU_DEAD: > + if (test_bit(cpu, cpu_clamping_mask)) { > + pr_err("cpu %lu dead but powerclamping thread is not\n", > + cpu); > + kthread_stop(*percpu_thread); > + } > + if (cpu == control_cpu) { > + control_cpu = smp_processor_id(); > + smp_mb(); > + } > + } > + > +exit_ok: > + return NOTIFY_OK; > +} > + > +static struct notifier_block powerclamp_cpu_notifier = { > + .notifier_call = powerclamp_cpu_callback, > +}; > + > +static int powerclamp_get_max_state(struct thermal_cooling_device *cdev, > + unsigned long *state) > +{ > + *state = MAX_TARGET_RATIO; > + > + return 0; > +} > + > +static int powerclamp_get_cur_state(struct thermal_cooling_device *cdev, > + unsigned long *state) > +{ > + if (true == clamping) > + *state = pkg_cstate_ratio_cur; > + else > + /* to save power, do not poll idle ratio while not clamping */ > + *state = -1; /* indicates invalid state */ > + > + return 0; > +} > + > +static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev, > + unsigned long new_target_ratio) > +{ > + int ret = 0; > + > + new_target_ratio = clamp(new_target_ratio, 0UL, > + (unsigned long) (MAX_TARGET_RATIO-1)); > + if (set_target_ratio == 0 && new_target_ratio > 0) { > + pr_info("Start idle injection to reduce power\n"); > + set_target_ratio = new_target_ratio; > + ret = start_power_clamp(); > + goto exit_set; > + } else if (set_target_ratio > 0 && new_target_ratio == 0) { > + pr_info("Stop forced idle injection\n"); > + set_target_ratio = 0; > + end_power_clamp(); > + } else /* adjust currently running */ { > + set_target_ratio = new_target_ratio; > + /* make new set_target_ratio visible to other cpus */ > + smp_mb(); > + } > + > +exit_set: > + return ret; > +} > + > +/* bind to generic thermal layer as cooling device*/ > +static struct thermal_cooling_device_ops powerclamp_cooling_ops = { > + .get_max_state = powerclamp_get_max_state, > + .get_cur_state = powerclamp_get_cur_state, > + .set_cur_state = powerclamp_set_cur_state, > +}; > + > +/* runs on Nehalem and later */ > +static const struct x86_cpu_id intel_powerclamp_ids[] = { > + { X86_VENDOR_INTEL, 6, 0x1a}, > + { X86_VENDOR_INTEL, 6, 0x1c}, > + { X86_VENDOR_INTEL, 6, 0x1e}, > + { X86_VENDOR_INTEL, 6, 0x1f}, > + { X86_VENDOR_INTEL, 6, 0x25}, > + { X86_VENDOR_INTEL, 6, 0x26}, > + { X86_VENDOR_INTEL, 6, 0x2a}, > + { X86_VENDOR_INTEL, 6, 0x2c}, > + { X86_VENDOR_INTEL, 6, 0x2d}, > + { X86_VENDOR_INTEL, 6, 0x2e}, > + { X86_VENDOR_INTEL, 6, 0x2f}, > + { X86_VENDOR_INTEL, 6, 0x3a}, > + {} > +}; > +MODULE_DEVICE_TABLE(x86cpu, intel_powerclamp_ids); > + > +static int powerclamp_probe(void) > +{ > + if (!x86_match_cpu(intel_powerclamp_ids)) { > + pr_err("Intel powerclamp does not run on family %d model %d\n", > + boot_cpu_data.x86, boot_cpu_data.x86_model); > + return -ENODEV; > + } > + if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC) || > + !boot_cpu_has(X86_FEATURE_CONSTANT_TSC) || > + !boot_cpu_has(X86_FEATURE_MWAIT) || > + !boot_cpu_has(X86_FEATURE_ARAT)) > + return -ENODEV; > + > + /* find the deepest mwait value */ > + find_target_mwait(); > + > + return 0; > +} > + > +static int powerclamp_debug_show(struct seq_file *m, void *unused) > +{ > + int i = 0; > + > + seq_printf(m, "controlling cpu: %d\n", control_cpu); > + seq_printf(m, "pct confidence steady dynamic (compensation)\n"); > + for (i = 0; i < MAX_TARGET_RATIO; i++) { > + seq_printf(m, "%d\t%lu\t%lu\t%lu\n", > + i, > + cal_data[i].confidence, > + cal_data[i].steady_comp, > + cal_data[i].dynamic_comp); > + } > + > + return 0; > +} > + > +static int powerclamp_debug_open(struct inode *inode, > + struct file *file) > +{ > + return single_open(file, powerclamp_debug_show, inode->i_private); > +} > + > +static const struct file_operations powerclamp_debug_fops = { > + .open = powerclamp_debug_open, > + .read = seq_read, > + .llseek = seq_lseek, > + .release = single_release, > + .owner = THIS_MODULE, > +}; > + > +static inline void powerclamp_create_debug_files(void) > +{ > + debug_dir = debugfs_create_dir("intel_powerclamp", NULL); > + if (!debug_dir) > + return; > + > + if (!debugfs_create_file("powerclamp_calib", S_IRUGO, debug_dir, > + cal_data, &powerclamp_debug_fops)) > + goto file_error; > + > + return; > + > +file_error: > + debugfs_remove_recursive(debug_dir); > +} > + > +static int powerclamp_init(void) > +{ > + int retval; > + int bitmap_size; > + > + bitmap_size = BITS_TO_LONGS(num_possible_cpus()) * sizeof(long); > + cpu_clamping_mask = kzalloc(bitmap_size, GFP_KERNEL); > + if (!cpu_clamping_mask) > + return -ENOMEM; > + > + /* probe cpu features and ids here */ > + retval = powerclamp_probe(); > + if (retval) > + return retval; > + /* set default limit, maybe adjusted during runtime based on feedback */ > + window_size = 2; > + register_hotcpu_notifier(&powerclamp_cpu_notifier); > + powerclamp_thread = alloc_percpu(struct task_struct *); > + cooling_dev = thermal_cooling_device_register("intel_powerclamp", NULL, > + &powerclamp_cooling_ops); > + if (IS_ERR(cooling_dev)) > + return -ENODEV; > + > + if (!duration) > + duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES); > + powerclamp_create_debug_files(); > + > + return 0; > +} > +module_init(powerclamp_init); > + > +static void powerclamp_exit(void) > +{ > + unregister_hotcpu_notifier(&powerclamp_cpu_notifier); > + end_power_clamp(); > + free_percpu(powerclamp_thread); > + thermal_cooling_device_unregister(cooling_dev); > + kfree(cpu_clamping_mask); > + > + cancel_delayed_work_sync(&poll_pkg_cstate_work); > + debugfs_remove_recursive(debug_dir); > +} > +module_exit(powerclamp_exit); > + > +MODULE_LICENSE("GPL"); > +MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>"); > +MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>"); > +MODULE_DESCRIPTION("Package Level C-state Idle Injection for Intel CPUs"); -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2013-01-16 at 05:11 -0800, Jacob Pan wrote: > Intel PowerClamp driver performs synchronized idle injection across > all online CPUs. The goal is to maintain a given package level C-state > ratio. > > Compared to other throttling methods already exist in the kernel, > such as ACPI PAD (taking CPUs offline) and clock modulation, this is often > more efficient in terms of performance per watt. > > Please refer to Documentation/thermal/intel_powerclamp.txt for more details. > > Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> applied to thermal -next. thanks, rui > --- > Documentation/thermal/intel_powerclamp.txt | 307 +++++++++++ > drivers/thermal/Kconfig | 10 + > drivers/thermal/Makefile | 2 + > drivers/thermal/intel_powerclamp.c | 788 ++++++++++++++++++++++++++++ > 4 files changed, 1107 insertions(+) > create mode 100644 Documentation/thermal/intel_powerclamp.txt > create mode 100644 drivers/thermal/intel_powerclamp.c > > diff --git a/Documentation/thermal/intel_powerclamp.txt b/Documentation/thermal/intel_powerclamp.txt > new file mode 100644 > index 0000000..332de4a > --- /dev/null > +++ b/Documentation/thermal/intel_powerclamp.txt > @@ -0,0 +1,307 @@ > + ======================= > + INTEL POWERCLAMP DRIVER > + ======================= > +By: Arjan van de Ven <arjan@linux.intel.com> > + Jacob Pan <jacob.jun.pan@linux.intel.com> > + > +Contents: > + (*) Introduction > + - Goals and Objectives > + > + (*) Theory of Operation > + - Idle Injection > + - Calibration > + > + (*) Performance Analysis > + - Effectiveness and Limitations > + - Power vs Performance > + - Scalability > + - Calibration > + - Comparison with Alternative Techniques > + > + (*) Usage and Interfaces > + - Generic Thermal Layer (sysfs) > + - Kernel APIs (TBD) > + > +============ > +INTRODUCTION > +============ > + > +Consider the situation where a system’s power consumption must be > +reduced at runtime, due to power budget, thermal constraint, or noise > +level, and where active cooling is not preferred. Software managed > +passive power reduction must be performed to prevent the hardware > +actions that are designed for catastrophic scenarios. > + > +Currently, P-states, T-states (clock modulation), and CPU offlining > +are used for CPU throttling. > + > +On Intel CPUs, C-states provide effective power reduction, but so far > +they’re only used opportunistically, based on workload. With the > +development of intel_powerclamp driver, the method of synchronizing > +idle injection across all online CPU threads was introduced. The goal > +is to achieve forced and controllable C-state residency. > + > +Test/Analysis has been made in the areas of power, performance, > +scalability, and user experience. In many cases, clear advantage is > +shown over taking the CPU offline or modulating the CPU clock. > + > + > +=================== > +THEORY OF OPERATION > +=================== > + > +Idle Injection > +-------------- > + > +On modern Intel processors (Nehalem or later), package level C-state > +residency is available in MSRs, thus also available to the kernel. > + > +These MSRs are: > + #define MSR_PKG_C2_RESIDENCY 0x60D > + #define MSR_PKG_C3_RESIDENCY 0x3F8 > + #define MSR_PKG_C6_RESIDENCY 0x3F9 > + #define MSR_PKG_C7_RESIDENCY 0x3FA > + > +If the kernel can also inject idle time to the system, then a > +closed-loop control system can be established that manages package > +level C-state. The intel_powerclamp driver is conceived as such a > +control system, where the target set point is a user-selected idle > +ratio (based on power reduction), and the error is the difference > +between the actual package level C-state residency ratio and the target idle > +ratio. > + > +Injection is controlled by high priority kernel threads, spawned for > +each online CPU. > + > +These kernel threads, with SCHED_FIFO class, are created to perform > +clamping actions of controlled duty ratio and duration. Each per-CPU > +thread synchronizes its idle time and duration, based on the rounding > +of jiffies, so accumulated errors can be prevented to avoid a jittery > +effect. Threads are also bound to the CPU such that they cannot be > +migrated, unless the CPU is taken offline. In this case, threads > +belong to the offlined CPUs will be terminated immediately. > + > +Running as SCHED_FIFO and relatively high priority, also allows such > +scheme to work for both preemptable and non-preemptable kernels. > +Alignment of idle time around jiffies ensures scalability for HZ > +values. This effect can be better visualized using a Perf timechart. > +The following diagram shows the behavior of kernel thread > +kidle_inject/cpu. During idle injection, it runs monitor/mwait idle > +for a given "duration", then relinquishes the CPU to other tasks, > +until the next time interval. > + > +The NOHZ schedule tick is disabled during idle time, but interrupts > +are not masked. Tests show that the extra wakeups from scheduler tick > +have a dramatic impact on the effectiveness of the powerclamp driver > +on large scale systems (Westmere system with 80 processors). > + > +CPU0 > + ____________ ____________ > +kidle_inject/0 | sleep | mwait | sleep | > + _________| |________| |_______ > + duration > +CPU1 > + ____________ ____________ > +kidle_inject/1 | sleep | mwait | sleep | > + _________| |________| |_______ > + ^ > + | > + | > + roundup(jiffies, interval) > + > +Only one CPU is allowed to collect statistics and update global > +control parameters. This CPU is referred to as the controlling CPU in > +this document. The controlling CPU is elected at runtime, with a > +policy that favors BSP, taking into account the possibility of a CPU > +hot-plug. > + > +In terms of dynamics of the idle control system, package level idle > +time is considered largely as a non-causal system where its behavior > +cannot be based on the past or current input. Therefore, the > +intel_powerclamp driver attempts to enforce the desired idle time > +instantly as given input (target idle ratio). After injection, > +powerclamp moniors the actual idle for a given time window and adjust > +the next injection accordingly to avoid over/under correction. > + > +When used in a causal control system, such as a temperature control, > +it is up to the user of this driver to implement algorithms where > +past samples and outputs are included in the feedback. For example, a > +PID-based thermal controller can use the powerclamp driver to > +maintain a desired target temperature, based on integral and > +derivative gains of the past samples. > + > + > + > +Calibration > +----------- > +During scalability testing, it is observed that synchronized actions > +among CPUs become challenging as the number of cores grows. This is > +also true for the ability of a system to enter package level C-states. > + > +To make sure the intel_powerclamp driver scales well, online > +calibration is implemented. The goals for doing such a calibration > +are: > + > +a) determine the effective range of idle injection ratio > +b) determine the amount of compensation needed at each target ratio > + > +Compensation to each target ratio consists of two parts: > + > + a) steady state error compensation > + This is to offset the error occurring when the system can > + enter idle without extra wakeups (such as external interrupts). > + > + b) dynamic error compensation > + When an excessive amount of wakeups occurs during idle, an > + additional idle ratio can be added to quiet interrupts, by > + slowing down CPU activities. > + > +A debugfs file is provided for the user to examine compensation > +progress and results, such as on a Westmere system. > +[jacob@nex01 ~]$ cat > +/sys/kernel/debug/intel_powerclamp/powerclamp_calib > +controlling cpu: 0 > +pct confidence steady dynamic (compensation) > +0 0 0 0 > +1 1 0 0 > +2 1 1 0 > +3 3 1 0 > +4 3 1 0 > +5 3 1 0 > +6 3 1 0 > +7 3 1 0 > +8 3 1 0 > +... > +30 3 2 0 > +31 3 2 0 > +32 3 1 0 > +33 3 2 0 > +34 3 1 0 > +35 3 2 0 > +36 3 1 0 > +37 3 2 0 > +38 3 1 0 > +39 3 2 0 > +40 3 3 0 > +41 3 1 0 > +42 3 2 0 > +43 3 1 0 > +44 3 1 0 > +45 3 2 0 > +46 3 3 0 > +47 3 0 0 > +48 3 2 0 > +49 3 3 0 > + > +Calibration occurs during runtime. No offline method is available. > +Steady state compensation is used only when confidence levels of all > +adjacent ratios have reached satisfactory level. A confidence level > +is accumulated based on clean data collected at runtime. Data > +collected during a period without extra interrupts is considered > +clean. > + > +To compensate for excessive amounts of wakeup during idle, additional > +idle time is injected when such a condition is detected. Currently, > +we have a simple algorithm to double the injection ratio. A possible > +enhancement might be to throttle the offending IRQ, such as delaying > +EOI for level triggered interrupts. But it is a challenge to be > +non-intrusive to the scheduler or the IRQ core code. > + > + > +CPU Online/Offline > +------------------ > +Per-CPU kernel threads are started/stopped upon receiving > +notifications of CPU hotplug activities. The intel_powerclamp driver > +keeps track of clamping kernel threads, even after they are migrated > +to other CPUs, after a CPU offline event. > + > + > +===================== > +Performance Analysis > +===================== > +This section describes the general performance data collected on > +multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P). > + > +Effectiveness and Limitations > +----------------------------- > +The maximum range that idle injection is allowed is capped at 50 > +percent. As mentioned earlier, since interrupts are allowed during > +forced idle time, excessive interrupts could result in less > +effectiveness. The extreme case would be doing a ping -f to generated > +flooded network interrupts without much CPU acknowledgement. In this > +case, little can be done from the idle injection threads. In most > +normal cases, such as scp a large file, applications can be throttled > +by the powerclamp driver, since slowing down the CPU also slows down > +network protocol processing, which in turn reduces interrupts. > + > +When control parameters change at runtime by the controlling CPU, it > +may take an additional period for the rest of the CPUs to catch up > +with the changes. During this time, idle injection is out of sync, > +thus not able to enter package C- states at the expected ratio. But > +this effect is minor, in that in most cases change to the target > +ratio is updated much less frequently than the idle injection > +frequency. > + > +Scalability > +----------- > +Tests also show a minor, but measurable, difference between the 4P/8P > +Ivy Bridge system and the 80P Westmere server under 50% idle ratio. > +More compensation is needed on Westmere for the same amount of > +target idle ratio. The compensation also increases as the idle ratio > +gets larger. The above reason constitutes the need for the > +calibration code. > + > +On the IVB 8P system, compared to an offline CPU, powerclamp can > +achieve up to 40% better performance per watt. (measured by a spin > +counter summed over per CPU counting threads spawned for all running > +CPUs). > + > +==================== > +Usage and Interfaces > +==================== > +The powerclamp driver is registered to the generic thermal layer as a > +cooling device. Currently, it’s not bound to any thermal zones. > + > +jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . * > +cur_state:0 > +max_state:50 > +type:intel_powerclamp > + > +Example usage: > +- To inject 25% idle time > +$ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state > +" > + > +If the system is not busy and has more than 25% idle time already, > +then the powerclamp driver will not start idle injection. Using Top > +will not show idle injection kernel threads. > + > +If the system is busy (spin test below) and has less than 25% natural > +idle time, powerclamp kernel threads will do idle injection, which > +appear running to the scheduler. But the overall system idle is still > +reflected. In this example, 24.1% idle is shown. This helps the > +system admin or user determine the cause of slowdown, when a > +powerclamp driver is in action. > + > + > +Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie > +Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st > +Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers > +Swap: 4087804k total, 0k used, 4087804k free, 945336k cached > + > + PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > + 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin > + 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0 > + 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3 > + 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1 > + 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2 > + 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox > + 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg > + 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz > + > +Tests have shown that by using the powerclamp driver as a cooling > +device, a PID based userspace thermal controller can manage to > +control CPU temperature effectively, when no other thermal influence > +is added. For example, a UltraBook user can compile the kernel under > +certain temperature (below most active trip points). > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig > index c2c77d1..7d90ab8 100644 > --- a/drivers/thermal/Kconfig > +++ b/drivers/thermal/Kconfig > @@ -122,4 +122,14 @@ config DB8500_CPUFREQ_COOLING > bound cpufreq cooling device turns active to set CPU frequency low to > cool down the CPU. > > +config INTEL_POWERCLAMP > + tristate "Intel PowerClamp idle injection driver" > + depends on THERMAL > + depends on X86 > + depends on CPU_SUP_INTEL > + help > + Enable this to enable Intel PowerClamp idle injection driver. This > + enforce idle time which results in more package C-state residency. The > + user interface is exposed via generic thermal framework. > + > endif > diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile > index d8da683..574f5f5 100644 > --- a/drivers/thermal/Makefile > +++ b/drivers/thermal/Makefile > @@ -18,3 +18,5 @@ obj-$(CONFIG_RCAR_THERMAL) += rcar_thermal.o > obj-$(CONFIG_EXYNOS_THERMAL) += exynos_thermal.o > obj-$(CONFIG_DB8500_THERMAL) += db8500_thermal.o > obj-$(CONFIG_DB8500_CPUFREQ_COOLING) += db8500_cpufreq_cooling.o > +obj-$(CONFIG_INTEL_POWERCLAMP) += intel_powerclamp.o > + > diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c > new file mode 100644 > index 0000000..81ebf87 > --- /dev/null > +++ b/drivers/thermal/intel_powerclamp.c > @@ -0,0 +1,788 @@ > +/* > + * intel_powerclamp.c - package c-state idle injection > + * > + * Copyright (c) 2012, Intel Corporation. > + * > + * Authors: > + * Arjan van de Ven <arjan@linux.intel.com> > + * Jacob Pan <jacob.jun.pan@linux.intel.com> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms and conditions of the GNU General Public License, > + * version 2, as published by the Free Software Foundation. > + * > + * This program is distributed in the hope it will be useful, but WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + * > + * You should have received a copy of the GNU General Public License along with > + * this program; if not, write to the Free Software Foundation, Inc., > + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. > + * > + * > + * TODO: > + * 1. better handle wakeup from external interrupts, currently a fixed > + * compensation is added to clamping duration when excessive amount > + * of wakeups are observed during idle time. the reason is that in > + * case of external interrupts without need for ack, clamping down > + * cpu in non-irq context does not reduce irq. for majority of the > + * cases, clamping down cpu does help reduce irq as well, we should > + * be able to differenciate the two cases and give a quantitative > + * solution for the irqs that we can control. perhaps based on > + * get_cpu_iowait_time_us() > + * > + * 2. synchronization with other hw blocks > + * > + * > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/module.h> > +#include <linux/kernel.h> > +#include <linux/delay.h> > +#include <linux/kthread.h> > +#include <linux/freezer.h> > +#include <linux/cpu.h> > +#include <linux/thermal.h> > +#include <linux/slab.h> > +#include <linux/tick.h> > +#include <linux/debugfs.h> > +#include <linux/seq_file.h> > + > +#include <asm/nmi.h> > +#include <asm/msr.h> > +#include <asm/mwait.h> > +#include <asm/cpu_device_id.h> > +#include <asm/idle.h> > +#include <asm/hardirq.h> > + > +#define MAX_TARGET_RATIO (50U) > +/* For each undisturbed clamping period (no extra wake ups during idle time), > + * we increment the confidence counter for the given target ratio. > + * CONFIDENCE_OK defines the level where runtime calibration results are > + * valid. > + */ > +#define CONFIDENCE_OK (3) > +/* Default idle injection duration, driver adjust sleep time to meet target > + * idle ratio. Similar to frequency modulation. > + */ > +#define DEFAULT_DURATION_JIFFIES (6) > + > +static unsigned int target_mwait; > +static struct dentry *debug_dir; > + > +/* user selected target */ > +static unsigned int set_target_ratio; > +static unsigned int current_ratio; > +static bool should_skip; > +static bool reduce_irq; > +static atomic_t idle_wakeup_counter; > +static unsigned int control_cpu; /* The cpu assigned to collect stat and update > + * control parameters. default to BSP but BSP > + * can be offlined. > + */ > +static bool clamping; > + > + > +static struct task_struct __percpu **powerclamp_thread; > +static struct thermal_cooling_device *cooling_dev; > +static unsigned long *cpu_clamping_mask; /* bit map for tracking per cpu > + * clamping thread > + */ > + > +static unsigned int duration; > +static unsigned int pkg_cstate_ratio_cur; > +static unsigned int window_size; > + > +static int duration_set(const char *arg, const struct kernel_param *kp) > +{ > + int ret = 0; > + unsigned long new_duration; > + > + ret = kstrtoul(arg, 10, &new_duration); > + if (ret) > + goto exit; > + if (new_duration > 25 || new_duration < 6) { > + pr_err("Out of recommended range %lu, between 6-25ms\n", > + new_duration); > + ret = -EINVAL; > + } > + > + duration = clamp(new_duration, 6ul, 25ul); > + smp_mb(); > + > +exit: > + > + return ret; > +} > + > +static struct kernel_param_ops duration_ops = { > + .set = duration_set, > + .get = param_get_int, > +}; > + > + > +module_param_cb(duration, &duration_ops, &duration, 0644); > +MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec."); > + > +struct powerclamp_calibration_data { > + unsigned long confidence; /* used for calibration, basically a counter > + * gets incremented each time a clamping > + * period is completed without extra wakeups > + * once that counter is reached given level, > + * compensation is deemed usable. > + */ > + unsigned long steady_comp; /* steady state compensation used when > + * no extra wakeups occurred. > + */ > + unsigned long dynamic_comp; /* compensate excessive wakeup from idle > + * mostly from external interrupts. > + */ > +}; > + > +static struct powerclamp_calibration_data cal_data[MAX_TARGET_RATIO]; > + > +static int window_size_set(const char *arg, const struct kernel_param *kp) > +{ > + int ret = 0; > + unsigned long new_window_size; > + > + ret = kstrtoul(arg, 10, &new_window_size); > + if (ret) > + goto exit_win; > + if (new_window_size > 10 || new_window_size < 2) { > + pr_err("Out of recommended window size %lu, between 2-10\n", > + new_window_size); > + ret = -EINVAL; > + } > + > + window_size = clamp(new_window_size, 2ul, 10ul); > + smp_mb(); > + > +exit_win: > + > + return ret; > +} > + > +static struct kernel_param_ops window_size_ops = { > + .set = window_size_set, > + .get = param_get_int, > +}; > + > +module_param_cb(window_size, &window_size_ops, &window_size, 0644); > +MODULE_PARM_DESC(window_size, "sliding window in number of clamping cycles\n" > + "\tpowerclamp controls idle ratio within this window. larger\n" > + "\twindow size results in slower response time but more smooth\n" > + "\tclamping results. default to 2."); > + > +static void find_target_mwait(void) > +{ > + unsigned int eax, ebx, ecx, edx; > + unsigned int highest_cstate = 0; > + unsigned int highest_subcstate = 0; > + int i; > + > + if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) > + return; > + > + cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); > + > + if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || > + !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) > + return; > + > + edx >>= MWAIT_SUBSTATE_SIZE; > + for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { > + if (edx & MWAIT_SUBSTATE_MASK) { > + highest_cstate = i; > + highest_subcstate = edx & MWAIT_SUBSTATE_MASK; > + } > + } > + target_mwait = (highest_cstate << MWAIT_SUBSTATE_SIZE) | > + (highest_subcstate - 1); > + > +} > + > +static u64 pkg_state_counter(void) > +{ > + u64 val; > + u64 count = 0; > + > + static bool skip_c2; > + static bool skip_c3; > + static bool skip_c6; > + static bool skip_c7; > + > + if (!skip_c2) { > + if (!rdmsrl_safe(MSR_PKG_C2_RESIDENCY, &val)) > + count += val; > + else > + skip_c2 = true; > + } > + > + if (!skip_c3) { > + if (!rdmsrl_safe(MSR_PKG_C3_RESIDENCY, &val)) > + count += val; > + else > + skip_c3 = true; > + } > + > + if (!skip_c6) { > + if (!rdmsrl_safe(MSR_PKG_C6_RESIDENCY, &val)) > + count += val; > + else > + skip_c6 = true; > + } > + > + if (!skip_c7) { > + if (!rdmsrl_safe(MSR_PKG_C7_RESIDENCY, &val)) > + count += val; > + else > + skip_c7 = true; > + } > + > + return count; > +} > + > +static void noop_timer(unsigned long foo) > +{ > + /* empty... just the fact that we get the interrupt wakes us up */ > +} > + > +static unsigned int get_compensation(int ratio) > +{ > + unsigned int comp = 0; > + > + /* we only use compensation if all adjacent ones are good */ > + if (ratio == 1 && > + cal_data[ratio].confidence >= CONFIDENCE_OK && > + cal_data[ratio + 1].confidence >= CONFIDENCE_OK && > + cal_data[ratio + 2].confidence >= CONFIDENCE_OK) { > + comp = (cal_data[ratio].steady_comp + > + cal_data[ratio + 1].steady_comp + > + cal_data[ratio + 2].steady_comp) / 3; > + } else if (ratio == MAX_TARGET_RATIO - 1 && > + cal_data[ratio].confidence >= CONFIDENCE_OK && > + cal_data[ratio - 1].confidence >= CONFIDENCE_OK && > + cal_data[ratio - 2].confidence >= CONFIDENCE_OK) { > + comp = (cal_data[ratio].steady_comp + > + cal_data[ratio - 1].steady_comp + > + cal_data[ratio - 2].steady_comp) / 3; > + } else if (cal_data[ratio].confidence >= CONFIDENCE_OK && > + cal_data[ratio - 1].confidence >= CONFIDENCE_OK && > + cal_data[ratio + 1].confidence >= CONFIDENCE_OK) { > + comp = (cal_data[ratio].steady_comp + > + cal_data[ratio - 1].steady_comp + > + cal_data[ratio + 1].steady_comp) / 3; > + } > + > + /* REVISIT: simple penalty of double idle injection */ > + if (reduce_irq) > + comp = ratio; > + /* do not exceed limit */ > + if (comp + ratio >= MAX_TARGET_RATIO) > + comp = MAX_TARGET_RATIO - ratio - 1; > + > + return comp; > +} > + > +static void adjust_compensation(int target_ratio, unsigned int win) > +{ > + int delta; > + struct powerclamp_calibration_data *d = &cal_data[target_ratio]; > + > + /* > + * adjust compensations if confidence level has not been reached or > + * there are too many wakeups during the last idle injection period, we > + * cannot trust the data for compensation. > + */ > + if (d->confidence >= CONFIDENCE_OK || > + atomic_read(&idle_wakeup_counter) > > + win * num_online_cpus()) > + return; > + > + delta = set_target_ratio - current_ratio; > + /* filter out bad data */ > + if (delta >= 0 && delta <= (1+target_ratio/10)) { > + if (d->steady_comp) > + d->steady_comp = > + roundup(delta+d->steady_comp, 2)/2; > + else > + d->steady_comp = delta; > + d->confidence++; > + } > +} > + > +static bool powerclamp_adjust_controls(unsigned int target_ratio, > + unsigned int guard, unsigned int win) > +{ > + static u64 msr_last, tsc_last; > + u64 msr_now, tsc_now; > + > + /* check result for the last window */ > + msr_now = pkg_state_counter(); > + rdtscll(tsc_now); > + > + /* calculate pkg cstate vs tsc ratio */ > + if (!msr_last || !tsc_last) > + current_ratio = 1; > + else if (tsc_now-tsc_last) > + current_ratio = 100*(msr_now-msr_last)/ > + (tsc_now-tsc_last); > + > + /* update record */ > + msr_last = msr_now; > + tsc_last = tsc_now; > + > + adjust_compensation(target_ratio, win); > + /* > + * too many external interrupts, set flag such > + * that we can take measure later. > + */ > + reduce_irq = atomic_read(&idle_wakeup_counter) >= > + 2 * win * num_online_cpus(); > + > + atomic_set(&idle_wakeup_counter, 0); > + /* if we are above target+guard, skip */ > + return set_target_ratio + guard <= current_ratio; > +} > + > +static int clamp_thread(void *arg) > +{ > + int cpunr = (unsigned long)arg; > + DEFINE_TIMER(wakeup_timer, noop_timer, 0, 0); > + static const struct sched_param param = { > + .sched_priority = MAX_USER_RT_PRIO/2, > + }; > + unsigned int count = 0; > + unsigned int target_ratio; > + > + set_bit(cpunr, cpu_clamping_mask); > + set_freezable(); > + init_timer_on_stack(&wakeup_timer); > + sched_setscheduler(current, SCHED_FIFO, ¶m); > + > + while (true == clamping && !kthread_should_stop() && > + cpu_online(cpunr)) { > + int sleeptime; > + unsigned long target_jiffies; > + unsigned int guard; > + unsigned int compensation = 0; > + int interval; /* jiffies to sleep for each attempt */ > + unsigned int duration_jiffies = msecs_to_jiffies(duration); > + unsigned int window_size_now; > + > + try_to_freeze(); > + /* > + * make sure user selected ratio does not take effect until > + * the next round. adjust target_ratio if user has changed > + * target such that we can converge quickly. > + */ > + target_ratio = set_target_ratio; > + guard = 1 + target_ratio/20; > + window_size_now = window_size; > + count++; > + > + /* > + * systems may have different ability to enter package level > + * c-states, thus we need to compensate the injected idle ratio > + * to achieve the actual target reported by the HW. > + */ > + compensation = get_compensation(target_ratio); > + interval = duration_jiffies*100/(target_ratio+compensation); > + > + /* align idle time */ > + target_jiffies = roundup(jiffies, interval); > + sleeptime = target_jiffies - jiffies; > + if (sleeptime <= 0) > + sleeptime = 1; > + schedule_timeout_interruptible(sleeptime); > + /* > + * only elected controlling cpu can collect stats and update > + * control parameters. > + */ > + if (cpunr == control_cpu && !(count%window_size_now)) { > + should_skip = > + powerclamp_adjust_controls(target_ratio, > + guard, window_size_now); > + smp_mb(); > + } > + > + if (should_skip) > + continue; > + > + target_jiffies = jiffies + duration_jiffies; > + mod_timer(&wakeup_timer, target_jiffies); > + if (unlikely(local_softirq_pending())) > + continue; > + /* > + * stop tick sched during idle time, interrupts are still > + * allowed. thus jiffies are updated properly. > + */ > + preempt_disable(); > + tick_nohz_idle_enter(); > + /* mwait until target jiffies is reached */ > + while (time_before(jiffies, target_jiffies)) { > + unsigned long ecx = 1; > + unsigned long eax = target_mwait; > + > + /* > + * REVISIT: may call enter_idle() to notify drivers who > + * can save power during cpu idle. same for exit_idle() > + */ > + local_touch_nmi(); > + stop_critical_timings(); > + __monitor((void *)¤t_thread_info()->flags, 0, 0); > + cpu_relax(); /* allow HT sibling to run */ > + __mwait(eax, ecx); > + start_critical_timings(); > + atomic_inc(&idle_wakeup_counter); > + } > + tick_nohz_idle_exit(); > + preempt_enable_no_resched(); > + } > + del_timer_sync(&wakeup_timer); > + clear_bit(cpunr, cpu_clamping_mask); > + > + return 0; > +} > + > +/* > + * 1 HZ polling while clamping is active, useful for userspace > + * to monitor actual idle ratio. > + */ > +static void poll_pkg_cstate(struct work_struct *dummy); > +static DECLARE_DELAYED_WORK(poll_pkg_cstate_work, poll_pkg_cstate); > +static void poll_pkg_cstate(struct work_struct *dummy) > +{ > + static u64 msr_last; > + static u64 tsc_last; > + static unsigned long jiffies_last; > + > + u64 msr_now; > + unsigned long jiffies_now; > + u64 tsc_now; > + > + msr_now = pkg_state_counter(); > + rdtscll(tsc_now); > + jiffies_now = jiffies; > + > + /* calculate pkg cstate vs tsc ratio */ > + if (!msr_last || !tsc_last) > + pkg_cstate_ratio_cur = 1; > + else { > + if (tsc_now - tsc_last) > + pkg_cstate_ratio_cur = 100 * (msr_now - msr_last)/ > + (tsc_now - tsc_last); > + } > + > + /* update record */ > + msr_last = msr_now; > + jiffies_last = jiffies_now; > + tsc_last = tsc_now; > + > + if (true == clamping) > + schedule_delayed_work(&poll_pkg_cstate_work, HZ); > +} > + > +static int start_power_clamp(void) > +{ > + unsigned long cpu; > + struct task_struct *thread; > + > + /* check if pkg cstate counter is completely 0, abort in this case */ > + if (!pkg_state_counter()) { > + pr_err("pkg cstate counter not functional, abort\n"); > + return -EINVAL; > + } > + > + set_target_ratio = clamp(set_target_ratio, 0U, MAX_TARGET_RATIO); > + /* prevent cpu hotplug */ > + get_online_cpus(); > + > + /* prefer BSP */ > + control_cpu = 0; > + if (!cpu_online(control_cpu)) > + control_cpu = smp_processor_id(); > + > + clamping = true; > + schedule_delayed_work(&poll_pkg_cstate_work, 0); > + > + /* start one thread per online cpu */ > + for_each_online_cpu(cpu) { > + struct task_struct **p = > + per_cpu_ptr(powerclamp_thread, cpu); > + > + thread = kthread_create_on_node(clamp_thread, > + (void *) cpu, > + cpu_to_node(cpu), > + "kidle_inject/%ld", cpu); > + /* bind to cpu here */ > + if (likely(!IS_ERR(thread))) { > + kthread_bind(thread, cpu); > + wake_up_process(thread); > + *p = thread; > + } > + > + } > + put_online_cpus(); > + > + return 0; > +} > + > +static void end_power_clamp(void) > +{ > + int i; > + struct task_struct *thread; > + > + clamping = false; > + /* > + * make clamping visible to other cpus and give per cpu clamping threads > + * sometime to exit, or gets killed later. > + */ > + smp_mb(); > + msleep(20); > + if (bitmap_weight(cpu_clamping_mask, num_possible_cpus())) { > + for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) { > + pr_debug("clamping thread for cpu %d alive, kill\n", i); > + thread = *per_cpu_ptr(powerclamp_thread, i); > + kthread_stop(thread); > + } > + } > +} > + > +static int powerclamp_cpu_callback(struct notifier_block *nfb, > + unsigned long action, void *hcpu) > +{ > + unsigned long cpu = (unsigned long)hcpu; > + struct task_struct *thread; > + struct task_struct **percpu_thread = > + per_cpu_ptr(powerclamp_thread, cpu); > + > + if (false == clamping) > + goto exit_ok; > + > + switch (action) { > + case CPU_ONLINE: > + thread = kthread_create_on_node(clamp_thread, > + (void *) cpu, > + cpu_to_node(cpu), > + "kidle_inject/%lu", cpu); > + if (likely(!IS_ERR(thread))) { > + kthread_bind(thread, cpu); > + wake_up_process(thread); > + *percpu_thread = thread; > + } > + /* prefer BSP as controlling CPU */ > + if (cpu == 0) { > + control_cpu = 0; > + smp_mb(); > + } > + break; > + case CPU_DEAD: > + if (test_bit(cpu, cpu_clamping_mask)) { > + pr_err("cpu %lu dead but powerclamping thread is not\n", > + cpu); > + kthread_stop(*percpu_thread); > + } > + if (cpu == control_cpu) { > + control_cpu = smp_processor_id(); > + smp_mb(); > + } > + } > + > +exit_ok: > + return NOTIFY_OK; > +} > + > +static struct notifier_block powerclamp_cpu_notifier = { > + .notifier_call = powerclamp_cpu_callback, > +}; > + > +static int powerclamp_get_max_state(struct thermal_cooling_device *cdev, > + unsigned long *state) > +{ > + *state = MAX_TARGET_RATIO; > + > + return 0; > +} > + > +static int powerclamp_get_cur_state(struct thermal_cooling_device *cdev, > + unsigned long *state) > +{ > + if (true == clamping) > + *state = pkg_cstate_ratio_cur; > + else > + /* to save power, do not poll idle ratio while not clamping */ > + *state = -1; /* indicates invalid state */ > + > + return 0; > +} > + > +static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev, > + unsigned long new_target_ratio) > +{ > + int ret = 0; > + > + new_target_ratio = clamp(new_target_ratio, 0UL, > + (unsigned long) (MAX_TARGET_RATIO-1)); > + if (set_target_ratio == 0 && new_target_ratio > 0) { > + pr_info("Start idle injection to reduce power\n"); > + set_target_ratio = new_target_ratio; > + ret = start_power_clamp(); > + goto exit_set; > + } else if (set_target_ratio > 0 && new_target_ratio == 0) { > + pr_info("Stop forced idle injection\n"); > + set_target_ratio = 0; > + end_power_clamp(); > + } else /* adjust currently running */ { > + set_target_ratio = new_target_ratio; > + /* make new set_target_ratio visible to other cpus */ > + smp_mb(); > + } > + > +exit_set: > + return ret; > +} > + > +/* bind to generic thermal layer as cooling device*/ > +static struct thermal_cooling_device_ops powerclamp_cooling_ops = { > + .get_max_state = powerclamp_get_max_state, > + .get_cur_state = powerclamp_get_cur_state, > + .set_cur_state = powerclamp_set_cur_state, > +}; > + > +/* runs on Nehalem and later */ > +static const struct x86_cpu_id intel_powerclamp_ids[] = { > + { X86_VENDOR_INTEL, 6, 0x1a}, > + { X86_VENDOR_INTEL, 6, 0x1c}, > + { X86_VENDOR_INTEL, 6, 0x1e}, > + { X86_VENDOR_INTEL, 6, 0x1f}, > + { X86_VENDOR_INTEL, 6, 0x25}, > + { X86_VENDOR_INTEL, 6, 0x26}, > + { X86_VENDOR_INTEL, 6, 0x2a}, > + { X86_VENDOR_INTEL, 6, 0x2c}, > + { X86_VENDOR_INTEL, 6, 0x2d}, > + { X86_VENDOR_INTEL, 6, 0x2e}, > + { X86_VENDOR_INTEL, 6, 0x2f}, > + { X86_VENDOR_INTEL, 6, 0x3a}, > + {} > +}; > +MODULE_DEVICE_TABLE(x86cpu, intel_powerclamp_ids); > + > +static int powerclamp_probe(void) > +{ > + if (!x86_match_cpu(intel_powerclamp_ids)) { > + pr_err("Intel powerclamp does not run on family %d model %d\n", > + boot_cpu_data.x86, boot_cpu_data.x86_model); > + return -ENODEV; > + } > + if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC) || > + !boot_cpu_has(X86_FEATURE_CONSTANT_TSC) || > + !boot_cpu_has(X86_FEATURE_MWAIT) || > + !boot_cpu_has(X86_FEATURE_ARAT)) > + return -ENODEV; > + > + /* find the deepest mwait value */ > + find_target_mwait(); > + > + return 0; > +} > + > +static int powerclamp_debug_show(struct seq_file *m, void *unused) > +{ > + int i = 0; > + > + seq_printf(m, "controlling cpu: %d\n", control_cpu); > + seq_printf(m, "pct confidence steady dynamic (compensation)\n"); > + for (i = 0; i < MAX_TARGET_RATIO; i++) { > + seq_printf(m, "%d\t%lu\t%lu\t%lu\n", > + i, > + cal_data[i].confidence, > + cal_data[i].steady_comp, > + cal_data[i].dynamic_comp); > + } > + > + return 0; > +} > + > +static int powerclamp_debug_open(struct inode *inode, > + struct file *file) > +{ > + return single_open(file, powerclamp_debug_show, inode->i_private); > +} > + > +static const struct file_operations powerclamp_debug_fops = { > + .open = powerclamp_debug_open, > + .read = seq_read, > + .llseek = seq_lseek, > + .release = single_release, > + .owner = THIS_MODULE, > +}; > + > +static inline void powerclamp_create_debug_files(void) > +{ > + debug_dir = debugfs_create_dir("intel_powerclamp", NULL); > + if (!debug_dir) > + return; > + > + if (!debugfs_create_file("powerclamp_calib", S_IRUGO, debug_dir, > + cal_data, &powerclamp_debug_fops)) > + goto file_error; > + > + return; > + > +file_error: > + debugfs_remove_recursive(debug_dir); > +} > + > +static int powerclamp_init(void) > +{ > + int retval; > + int bitmap_size; > + > + bitmap_size = BITS_TO_LONGS(num_possible_cpus()) * sizeof(long); > + cpu_clamping_mask = kzalloc(bitmap_size, GFP_KERNEL); > + if (!cpu_clamping_mask) > + return -ENOMEM; > + > + /* probe cpu features and ids here */ > + retval = powerclamp_probe(); > + if (retval) > + return retval; > + /* set default limit, maybe adjusted during runtime based on feedback */ > + window_size = 2; > + register_hotcpu_notifier(&powerclamp_cpu_notifier); > + powerclamp_thread = alloc_percpu(struct task_struct *); > + cooling_dev = thermal_cooling_device_register("intel_powerclamp", NULL, > + &powerclamp_cooling_ops); > + if (IS_ERR(cooling_dev)) > + return -ENODEV; > + > + if (!duration) > + duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES); > + powerclamp_create_debug_files(); > + > + return 0; > +} > +module_init(powerclamp_init); > + > +static void powerclamp_exit(void) > +{ > + unregister_hotcpu_notifier(&powerclamp_cpu_notifier); > + end_power_clamp(); > + free_percpu(powerclamp_thread); > + thermal_cooling_device_unregister(cooling_dev); > + kfree(cpu_clamping_mask); > + > + cancel_delayed_work_sync(&poll_pkg_cstate_work); > + debugfs_remove_recursive(debug_dir); > +} > +module_exit(powerclamp_exit); > + > +MODULE_LICENSE("GPL"); > +MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>"); > +MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>"); > +MODULE_DESCRIPTION("Package Level C-state Idle Injection for Intel CPUs"); -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/thermal/intel_powerclamp.txt b/Documentation/thermal/intel_powerclamp.txt new file mode 100644 index 0000000..332de4a --- /dev/null +++ b/Documentation/thermal/intel_powerclamp.txt @@ -0,0 +1,307 @@ + ======================= + INTEL POWERCLAMP DRIVER + ======================= +By: Arjan van de Ven <arjan@linux.intel.com> + Jacob Pan <jacob.jun.pan@linux.intel.com> + +Contents: + (*) Introduction + - Goals and Objectives + + (*) Theory of Operation + - Idle Injection + - Calibration + + (*) Performance Analysis + - Effectiveness and Limitations + - Power vs Performance + - Scalability + - Calibration + - Comparison with Alternative Techniques + + (*) Usage and Interfaces + - Generic Thermal Layer (sysfs) + - Kernel APIs (TBD) + +============ +INTRODUCTION +============ + +Consider the situation where a system’s power consumption must be +reduced at runtime, due to power budget, thermal constraint, or noise +level, and where active cooling is not preferred. Software managed +passive power reduction must be performed to prevent the hardware +actions that are designed for catastrophic scenarios. + +Currently, P-states, T-states (clock modulation), and CPU offlining +are used for CPU throttling. + +On Intel CPUs, C-states provide effective power reduction, but so far +they’re only used opportunistically, based on workload. With the +development of intel_powerclamp driver, the method of synchronizing +idle injection across all online CPU threads was introduced. The goal +is to achieve forced and controllable C-state residency. + +Test/Analysis has been made in the areas of power, performance, +scalability, and user experience. In many cases, clear advantage is +shown over taking the CPU offline or modulating the CPU clock. + + +=================== +THEORY OF OPERATION +=================== + +Idle Injection +-------------- + +On modern Intel processors (Nehalem or later), package level C-state +residency is available in MSRs, thus also available to the kernel. + +These MSRs are: + #define MSR_PKG_C2_RESIDENCY 0x60D + #define MSR_PKG_C3_RESIDENCY 0x3F8 + #define MSR_PKG_C6_RESIDENCY 0x3F9 + #define MSR_PKG_C7_RESIDENCY 0x3FA + +If the kernel can also inject idle time to the system, then a +closed-loop control system can be established that manages package +level C-state. The intel_powerclamp driver is conceived as such a +control system, where the target set point is a user-selected idle +ratio (based on power reduction), and the error is the difference +between the actual package level C-state residency ratio and the target idle +ratio. + +Injection is controlled by high priority kernel threads, spawned for +each online CPU. + +These kernel threads, with SCHED_FIFO class, are created to perform +clamping actions of controlled duty ratio and duration. Each per-CPU +thread synchronizes its idle time and duration, based on the rounding +of jiffies, so accumulated errors can be prevented to avoid a jittery +effect. Threads are also bound to the CPU such that they cannot be +migrated, unless the CPU is taken offline. In this case, threads +belong to the offlined CPUs will be terminated immediately. + +Running as SCHED_FIFO and relatively high priority, also allows such +scheme to work for both preemptable and non-preemptable kernels. +Alignment of idle time around jiffies ensures scalability for HZ +values. This effect can be better visualized using a Perf timechart. +The following diagram shows the behavior of kernel thread +kidle_inject/cpu. During idle injection, it runs monitor/mwait idle +for a given "duration", then relinquishes the CPU to other tasks, +until the next time interval. + +The NOHZ schedule tick is disabled during idle time, but interrupts +are not masked. Tests show that the extra wakeups from scheduler tick +have a dramatic impact on the effectiveness of the powerclamp driver +on large scale systems (Westmere system with 80 processors). + +CPU0 + ____________ ____________ +kidle_inject/0 | sleep | mwait | sleep | + _________| |________| |_______ + duration +CPU1 + ____________ ____________ +kidle_inject/1 | sleep | mwait | sleep | + _________| |________| |_______ + ^ + | + | + roundup(jiffies, interval) + +Only one CPU is allowed to collect statistics and update global +control parameters. This CPU is referred to as the controlling CPU in +this document. The controlling CPU is elected at runtime, with a +policy that favors BSP, taking into account the possibility of a CPU +hot-plug. + +In terms of dynamics of the idle control system, package level idle +time is considered largely as a non-causal system where its behavior +cannot be based on the past or current input. Therefore, the +intel_powerclamp driver attempts to enforce the desired idle time +instantly as given input (target idle ratio). After injection, +powerclamp moniors the actual idle for a given time window and adjust +the next injection accordingly to avoid over/under correction. + +When used in a causal control system, such as a temperature control, +it is up to the user of this driver to implement algorithms where +past samples and outputs are included in the feedback. For example, a +PID-based thermal controller can use the powerclamp driver to +maintain a desired target temperature, based on integral and +derivative gains of the past samples. + + + +Calibration +----------- +During scalability testing, it is observed that synchronized actions +among CPUs become challenging as the number of cores grows. This is +also true for the ability of a system to enter package level C-states. + +To make sure the intel_powerclamp driver scales well, online +calibration is implemented. The goals for doing such a calibration +are: + +a) determine the effective range of idle injection ratio +b) determine the amount of compensation needed at each target ratio + +Compensation to each target ratio consists of two parts: + + a) steady state error compensation + This is to offset the error occurring when the system can + enter idle without extra wakeups (such as external interrupts). + + b) dynamic error compensation + When an excessive amount of wakeups occurs during idle, an + additional idle ratio can be added to quiet interrupts, by + slowing down CPU activities. + +A debugfs file is provided for the user to examine compensation +progress and results, such as on a Westmere system. +[jacob@nex01 ~]$ cat +/sys/kernel/debug/intel_powerclamp/powerclamp_calib +controlling cpu: 0 +pct confidence steady dynamic (compensation) +0 0 0 0 +1 1 0 0 +2 1 1 0 +3 3 1 0 +4 3 1 0 +5 3 1 0 +6 3 1 0 +7 3 1 0 +8 3 1 0 +... +30 3 2 0 +31 3 2 0 +32 3 1 0 +33 3 2 0 +34 3 1 0 +35 3 2 0 +36 3 1 0 +37 3 2 0 +38 3 1 0 +39 3 2 0 +40 3 3 0 +41 3 1 0 +42 3 2 0 +43 3 1 0 +44 3 1 0 +45 3 2 0 +46 3 3 0 +47 3 0 0 +48 3 2 0 +49 3 3 0 + +Calibration occurs during runtime. No offline method is available. +Steady state compensation is used only when confidence levels of all +adjacent ratios have reached satisfactory level. A confidence level +is accumulated based on clean data collected at runtime. Data +collected during a period without extra interrupts is considered +clean. + +To compensate for excessive amounts of wakeup during idle, additional +idle time is injected when such a condition is detected. Currently, +we have a simple algorithm to double the injection ratio. A possible +enhancement might be to throttle the offending IRQ, such as delaying +EOI for level triggered interrupts. But it is a challenge to be +non-intrusive to the scheduler or the IRQ core code. + + +CPU Online/Offline +------------------ +Per-CPU kernel threads are started/stopped upon receiving +notifications of CPU hotplug activities. The intel_powerclamp driver +keeps track of clamping kernel threads, even after they are migrated +to other CPUs, after a CPU offline event. + + +===================== +Performance Analysis +===================== +This section describes the general performance data collected on +multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P). + +Effectiveness and Limitations +----------------------------- +The maximum range that idle injection is allowed is capped at 50 +percent. As mentioned earlier, since interrupts are allowed during +forced idle time, excessive interrupts could result in less +effectiveness. The extreme case would be doing a ping -f to generated +flooded network interrupts without much CPU acknowledgement. In this +case, little can be done from the idle injection threads. In most +normal cases, such as scp a large file, applications can be throttled +by the powerclamp driver, since slowing down the CPU also slows down +network protocol processing, which in turn reduces interrupts. + +When control parameters change at runtime by the controlling CPU, it +may take an additional period for the rest of the CPUs to catch up +with the changes. During this time, idle injection is out of sync, +thus not able to enter package C- states at the expected ratio. But +this effect is minor, in that in most cases change to the target +ratio is updated much less frequently than the idle injection +frequency. + +Scalability +----------- +Tests also show a minor, but measurable, difference between the 4P/8P +Ivy Bridge system and the 80P Westmere server under 50% idle ratio. +More compensation is needed on Westmere for the same amount of +target idle ratio. The compensation also increases as the idle ratio +gets larger. The above reason constitutes the need for the +calibration code. + +On the IVB 8P system, compared to an offline CPU, powerclamp can +achieve up to 40% better performance per watt. (measured by a spin +counter summed over per CPU counting threads spawned for all running +CPUs). + +==================== +Usage and Interfaces +==================== +The powerclamp driver is registered to the generic thermal layer as a +cooling device. Currently, it’s not bound to any thermal zones. + +jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . * +cur_state:0 +max_state:50 +type:intel_powerclamp + +Example usage: +- To inject 25% idle time +$ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state +" + +If the system is not busy and has more than 25% idle time already, +then the powerclamp driver will not start idle injection. Using Top +will not show idle injection kernel threads. + +If the system is busy (spin test below) and has less than 25% natural +idle time, powerclamp kernel threads will do idle injection, which +appear running to the scheduler. But the overall system idle is still +reflected. In this example, 24.1% idle is shown. This helps the +system admin or user determine the cause of slowdown, when a +powerclamp driver is in action. + + +Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie +Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st +Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers +Swap: 4087804k total, 0k used, 4087804k free, 945336k cached + + PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND + 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin + 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0 + 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3 + 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1 + 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2 + 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox + 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg + 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz + +Tests have shown that by using the powerclamp driver as a cooling +device, a PID based userspace thermal controller can manage to +control CPU temperature effectively, when no other thermal influence +is added. For example, a UltraBook user can compile the kernel under +certain temperature (below most active trip points). diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig index c2c77d1..7d90ab8 100644 --- a/drivers/thermal/Kconfig +++ b/drivers/thermal/Kconfig @@ -122,4 +122,14 @@ config DB8500_CPUFREQ_COOLING bound cpufreq cooling device turns active to set CPU frequency low to cool down the CPU. +config INTEL_POWERCLAMP + tristate "Intel PowerClamp idle injection driver" + depends on THERMAL + depends on X86 + depends on CPU_SUP_INTEL + help + Enable this to enable Intel PowerClamp idle injection driver. This + enforce idle time which results in more package C-state residency. The + user interface is exposed via generic thermal framework. + endif diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile index d8da683..574f5f5 100644 --- a/drivers/thermal/Makefile +++ b/drivers/thermal/Makefile @@ -18,3 +18,5 @@ obj-$(CONFIG_RCAR_THERMAL) += rcar_thermal.o obj-$(CONFIG_EXYNOS_THERMAL) += exynos_thermal.o obj-$(CONFIG_DB8500_THERMAL) += db8500_thermal.o obj-$(CONFIG_DB8500_CPUFREQ_COOLING) += db8500_cpufreq_cooling.o +obj-$(CONFIG_INTEL_POWERCLAMP) += intel_powerclamp.o + diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c new file mode 100644 index 0000000..81ebf87 --- /dev/null +++ b/drivers/thermal/intel_powerclamp.c @@ -0,0 +1,788 @@ +/* + * intel_powerclamp.c - package c-state idle injection + * + * Copyright (c) 2012, Intel Corporation. + * + * Authors: + * Arjan van de Ven <arjan@linux.intel.com> + * Jacob Pan <jacob.jun.pan@linux.intel.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * You should have received a copy of the GNU General Public License along with + * this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. + * + * + * TODO: + * 1. better handle wakeup from external interrupts, currently a fixed + * compensation is added to clamping duration when excessive amount + * of wakeups are observed during idle time. the reason is that in + * case of external interrupts without need for ack, clamping down + * cpu in non-irq context does not reduce irq. for majority of the + * cases, clamping down cpu does help reduce irq as well, we should + * be able to differenciate the two cases and give a quantitative + * solution for the irqs that we can control. perhaps based on + * get_cpu_iowait_time_us() + * + * 2. synchronization with other hw blocks + * + * + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/delay.h> +#include <linux/kthread.h> +#include <linux/freezer.h> +#include <linux/cpu.h> +#include <linux/thermal.h> +#include <linux/slab.h> +#include <linux/tick.h> +#include <linux/debugfs.h> +#include <linux/seq_file.h> + +#include <asm/nmi.h> +#include <asm/msr.h> +#include <asm/mwait.h> +#include <asm/cpu_device_id.h> +#include <asm/idle.h> +#include <asm/hardirq.h> + +#define MAX_TARGET_RATIO (50U) +/* For each undisturbed clamping period (no extra wake ups during idle time), + * we increment the confidence counter for the given target ratio. + * CONFIDENCE_OK defines the level where runtime calibration results are + * valid. + */ +#define CONFIDENCE_OK (3) +/* Default idle injection duration, driver adjust sleep time to meet target + * idle ratio. Similar to frequency modulation. + */ +#define DEFAULT_DURATION_JIFFIES (6) + +static unsigned int target_mwait; +static struct dentry *debug_dir; + +/* user selected target */ +static unsigned int set_target_ratio; +static unsigned int current_ratio; +static bool should_skip; +static bool reduce_irq; +static atomic_t idle_wakeup_counter; +static unsigned int control_cpu; /* The cpu assigned to collect stat and update + * control parameters. default to BSP but BSP + * can be offlined. + */ +static bool clamping; + + +static struct task_struct __percpu **powerclamp_thread; +static struct thermal_cooling_device *cooling_dev; +static unsigned long *cpu_clamping_mask; /* bit map for tracking per cpu + * clamping thread + */ + +static unsigned int duration; +static unsigned int pkg_cstate_ratio_cur; +static unsigned int window_size; + +static int duration_set(const char *arg, const struct kernel_param *kp) +{ + int ret = 0; + unsigned long new_duration; + + ret = kstrtoul(arg, 10, &new_duration); + if (ret) + goto exit; + if (new_duration > 25 || new_duration < 6) { + pr_err("Out of recommended range %lu, between 6-25ms\n", + new_duration); + ret = -EINVAL; + } + + duration = clamp(new_duration, 6ul, 25ul); + smp_mb(); + +exit: + + return ret; +} + +static struct kernel_param_ops duration_ops = { + .set = duration_set, + .get = param_get_int, +}; + + +module_param_cb(duration, &duration_ops, &duration, 0644); +MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec."); + +struct powerclamp_calibration_data { + unsigned long confidence; /* used for calibration, basically a counter + * gets incremented each time a clamping + * period is completed without extra wakeups + * once that counter is reached given level, + * compensation is deemed usable. + */ + unsigned long steady_comp; /* steady state compensation used when + * no extra wakeups occurred. + */ + unsigned long dynamic_comp; /* compensate excessive wakeup from idle + * mostly from external interrupts. + */ +}; + +static struct powerclamp_calibration_data cal_data[MAX_TARGET_RATIO]; + +static int window_size_set(const char *arg, const struct kernel_param *kp) +{ + int ret = 0; + unsigned long new_window_size; + + ret = kstrtoul(arg, 10, &new_window_size); + if (ret) + goto exit_win; + if (new_window_size > 10 || new_window_size < 2) { + pr_err("Out of recommended window size %lu, between 2-10\n", + new_window_size); + ret = -EINVAL; + } + + window_size = clamp(new_window_size, 2ul, 10ul); + smp_mb(); + +exit_win: + + return ret; +} + +static struct kernel_param_ops window_size_ops = { + .set = window_size_set, + .get = param_get_int, +}; + +module_param_cb(window_size, &window_size_ops, &window_size, 0644); +MODULE_PARM_DESC(window_size, "sliding window in number of clamping cycles\n" + "\tpowerclamp controls idle ratio within this window. larger\n" + "\twindow size results in slower response time but more smooth\n" + "\tclamping results. default to 2."); + +static void find_target_mwait(void) +{ + unsigned int eax, ebx, ecx, edx; + unsigned int highest_cstate = 0; + unsigned int highest_subcstate = 0; + int i; + + if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) + return; + + cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); + + if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || + !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) + return; + + edx >>= MWAIT_SUBSTATE_SIZE; + for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { + if (edx & MWAIT_SUBSTATE_MASK) { + highest_cstate = i; + highest_subcstate = edx & MWAIT_SUBSTATE_MASK; + } + } + target_mwait = (highest_cstate << MWAIT_SUBSTATE_SIZE) | + (highest_subcstate - 1); + +} + +static u64 pkg_state_counter(void) +{ + u64 val; + u64 count = 0; + + static bool skip_c2; + static bool skip_c3; + static bool skip_c6; + static bool skip_c7; + + if (!skip_c2) { + if (!rdmsrl_safe(MSR_PKG_C2_RESIDENCY, &val)) + count += val; + else + skip_c2 = true; + } + + if (!skip_c3) { + if (!rdmsrl_safe(MSR_PKG_C3_RESIDENCY, &val)) + count += val; + else + skip_c3 = true; + } + + if (!skip_c6) { + if (!rdmsrl_safe(MSR_PKG_C6_RESIDENCY, &val)) + count += val; + else + skip_c6 = true; + } + + if (!skip_c7) { + if (!rdmsrl_safe(MSR_PKG_C7_RESIDENCY, &val)) + count += val; + else + skip_c7 = true; + } + + return count; +} + +static void noop_timer(unsigned long foo) +{ + /* empty... just the fact that we get the interrupt wakes us up */ +} + +static unsigned int get_compensation(int ratio) +{ + unsigned int comp = 0; + + /* we only use compensation if all adjacent ones are good */ + if (ratio == 1 && + cal_data[ratio].confidence >= CONFIDENCE_OK && + cal_data[ratio + 1].confidence >= CONFIDENCE_OK && + cal_data[ratio + 2].confidence >= CONFIDENCE_OK) { + comp = (cal_data[ratio].steady_comp + + cal_data[ratio + 1].steady_comp + + cal_data[ratio + 2].steady_comp) / 3; + } else if (ratio == MAX_TARGET_RATIO - 1 && + cal_data[ratio].confidence >= CONFIDENCE_OK && + cal_data[ratio - 1].confidence >= CONFIDENCE_OK && + cal_data[ratio - 2].confidence >= CONFIDENCE_OK) { + comp = (cal_data[ratio].steady_comp + + cal_data[ratio - 1].steady_comp + + cal_data[ratio - 2].steady_comp) / 3; + } else if (cal_data[ratio].confidence >= CONFIDENCE_OK && + cal_data[ratio - 1].confidence >= CONFIDENCE_OK && + cal_data[ratio + 1].confidence >= CONFIDENCE_OK) { + comp = (cal_data[ratio].steady_comp + + cal_data[ratio - 1].steady_comp + + cal_data[ratio + 1].steady_comp) / 3; + } + + /* REVISIT: simple penalty of double idle injection */ + if (reduce_irq) + comp = ratio; + /* do not exceed limit */ + if (comp + ratio >= MAX_TARGET_RATIO) + comp = MAX_TARGET_RATIO - ratio - 1; + + return comp; +} + +static void adjust_compensation(int target_ratio, unsigned int win) +{ + int delta; + struct powerclamp_calibration_data *d = &cal_data[target_ratio]; + + /* + * adjust compensations if confidence level has not been reached or + * there are too many wakeups during the last idle injection period, we + * cannot trust the data for compensation. + */ + if (d->confidence >= CONFIDENCE_OK || + atomic_read(&idle_wakeup_counter) > + win * num_online_cpus()) + return; + + delta = set_target_ratio - current_ratio; + /* filter out bad data */ + if (delta >= 0 && delta <= (1+target_ratio/10)) { + if (d->steady_comp) + d->steady_comp = + roundup(delta+d->steady_comp, 2)/2; + else + d->steady_comp = delta; + d->confidence++; + } +} + +static bool powerclamp_adjust_controls(unsigned int target_ratio, + unsigned int guard, unsigned int win) +{ + static u64 msr_last, tsc_last; + u64 msr_now, tsc_now; + + /* check result for the last window */ + msr_now = pkg_state_counter(); + rdtscll(tsc_now); + + /* calculate pkg cstate vs tsc ratio */ + if (!msr_last || !tsc_last) + current_ratio = 1; + else if (tsc_now-tsc_last) + current_ratio = 100*(msr_now-msr_last)/ + (tsc_now-tsc_last); + + /* update record */ + msr_last = msr_now; + tsc_last = tsc_now; + + adjust_compensation(target_ratio, win); + /* + * too many external interrupts, set flag such + * that we can take measure later. + */ + reduce_irq = atomic_read(&idle_wakeup_counter) >= + 2 * win * num_online_cpus(); + + atomic_set(&idle_wakeup_counter, 0); + /* if we are above target+guard, skip */ + return set_target_ratio + guard <= current_ratio; +} + +static int clamp_thread(void *arg) +{ + int cpunr = (unsigned long)arg; + DEFINE_TIMER(wakeup_timer, noop_timer, 0, 0); + static const struct sched_param param = { + .sched_priority = MAX_USER_RT_PRIO/2, + }; + unsigned int count = 0; + unsigned int target_ratio; + + set_bit(cpunr, cpu_clamping_mask); + set_freezable(); + init_timer_on_stack(&wakeup_timer); + sched_setscheduler(current, SCHED_FIFO, ¶m); + + while (true == clamping && !kthread_should_stop() && + cpu_online(cpunr)) { + int sleeptime; + unsigned long target_jiffies; + unsigned int guard; + unsigned int compensation = 0; + int interval; /* jiffies to sleep for each attempt */ + unsigned int duration_jiffies = msecs_to_jiffies(duration); + unsigned int window_size_now; + + try_to_freeze(); + /* + * make sure user selected ratio does not take effect until + * the next round. adjust target_ratio if user has changed + * target such that we can converge quickly. + */ + target_ratio = set_target_ratio; + guard = 1 + target_ratio/20; + window_size_now = window_size; + count++; + + /* + * systems may have different ability to enter package level + * c-states, thus we need to compensate the injected idle ratio + * to achieve the actual target reported by the HW. + */ + compensation = get_compensation(target_ratio); + interval = duration_jiffies*100/(target_ratio+compensation); + + /* align idle time */ + target_jiffies = roundup(jiffies, interval); + sleeptime = target_jiffies - jiffies; + if (sleeptime <= 0) + sleeptime = 1; + schedule_timeout_interruptible(sleeptime); + /* + * only elected controlling cpu can collect stats and update + * control parameters. + */ + if (cpunr == control_cpu && !(count%window_size_now)) { + should_skip = + powerclamp_adjust_controls(target_ratio, + guard, window_size_now); + smp_mb(); + } + + if (should_skip) + continue; + + target_jiffies = jiffies + duration_jiffies; + mod_timer(&wakeup_timer, target_jiffies); + if (unlikely(local_softirq_pending())) + continue; + /* + * stop tick sched during idle time, interrupts are still + * allowed. thus jiffies are updated properly. + */ + preempt_disable(); + tick_nohz_idle_enter(); + /* mwait until target jiffies is reached */ + while (time_before(jiffies, target_jiffies)) { + unsigned long ecx = 1; + unsigned long eax = target_mwait; + + /* + * REVISIT: may call enter_idle() to notify drivers who + * can save power during cpu idle. same for exit_idle() + */ + local_touch_nmi(); + stop_critical_timings(); + __monitor((void *)¤t_thread_info()->flags, 0, 0); + cpu_relax(); /* allow HT sibling to run */ + __mwait(eax, ecx); + start_critical_timings(); + atomic_inc(&idle_wakeup_counter); + } + tick_nohz_idle_exit(); + preempt_enable_no_resched(); + } + del_timer_sync(&wakeup_timer); + clear_bit(cpunr, cpu_clamping_mask); + + return 0; +} + +/* + * 1 HZ polling while clamping is active, useful for userspace + * to monitor actual idle ratio. + */ +static void poll_pkg_cstate(struct work_struct *dummy); +static DECLARE_DELAYED_WORK(poll_pkg_cstate_work, poll_pkg_cstate); +static void poll_pkg_cstate(struct work_struct *dummy) +{ + static u64 msr_last; + static u64 tsc_last; + static unsigned long jiffies_last; + + u64 msr_now; + unsigned long jiffies_now; + u64 tsc_now; + + msr_now = pkg_state_counter(); + rdtscll(tsc_now); + jiffies_now = jiffies; + + /* calculate pkg cstate vs tsc ratio */ + if (!msr_last || !tsc_last) + pkg_cstate_ratio_cur = 1; + else { + if (tsc_now - tsc_last) + pkg_cstate_ratio_cur = 100 * (msr_now - msr_last)/ + (tsc_now - tsc_last); + } + + /* update record */ + msr_last = msr_now; + jiffies_last = jiffies_now; + tsc_last = tsc_now; + + if (true == clamping) + schedule_delayed_work(&poll_pkg_cstate_work, HZ); +} + +static int start_power_clamp(void) +{ + unsigned long cpu; + struct task_struct *thread; + + /* check if pkg cstate counter is completely 0, abort in this case */ + if (!pkg_state_counter()) { + pr_err("pkg cstate counter not functional, abort\n"); + return -EINVAL; + } + + set_target_ratio = clamp(set_target_ratio, 0U, MAX_TARGET_RATIO); + /* prevent cpu hotplug */ + get_online_cpus(); + + /* prefer BSP */ + control_cpu = 0; + if (!cpu_online(control_cpu)) + control_cpu = smp_processor_id(); + + clamping = true; + schedule_delayed_work(&poll_pkg_cstate_work, 0); + + /* start one thread per online cpu */ + for_each_online_cpu(cpu) { + struct task_struct **p = + per_cpu_ptr(powerclamp_thread, cpu); + + thread = kthread_create_on_node(clamp_thread, + (void *) cpu, + cpu_to_node(cpu), + "kidle_inject/%ld", cpu); + /* bind to cpu here */ + if (likely(!IS_ERR(thread))) { + kthread_bind(thread, cpu); + wake_up_process(thread); + *p = thread; + } + + } + put_online_cpus(); + + return 0; +} + +static void end_power_clamp(void) +{ + int i; + struct task_struct *thread; + + clamping = false; + /* + * make clamping visible to other cpus and give per cpu clamping threads + * sometime to exit, or gets killed later. + */ + smp_mb(); + msleep(20); + if (bitmap_weight(cpu_clamping_mask, num_possible_cpus())) { + for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) { + pr_debug("clamping thread for cpu %d alive, kill\n", i); + thread = *per_cpu_ptr(powerclamp_thread, i); + kthread_stop(thread); + } + } +} + +static int powerclamp_cpu_callback(struct notifier_block *nfb, + unsigned long action, void *hcpu) +{ + unsigned long cpu = (unsigned long)hcpu; + struct task_struct *thread; + struct task_struct **percpu_thread = + per_cpu_ptr(powerclamp_thread, cpu); + + if (false == clamping) + goto exit_ok; + + switch (action) { + case CPU_ONLINE: + thread = kthread_create_on_node(clamp_thread, + (void *) cpu, + cpu_to_node(cpu), + "kidle_inject/%lu", cpu); + if (likely(!IS_ERR(thread))) { + kthread_bind(thread, cpu); + wake_up_process(thread); + *percpu_thread = thread; + } + /* prefer BSP as controlling CPU */ + if (cpu == 0) { + control_cpu = 0; + smp_mb(); + } + break; + case CPU_DEAD: + if (test_bit(cpu, cpu_clamping_mask)) { + pr_err("cpu %lu dead but powerclamping thread is not\n", + cpu); + kthread_stop(*percpu_thread); + } + if (cpu == control_cpu) { + control_cpu = smp_processor_id(); + smp_mb(); + } + } + +exit_ok: + return NOTIFY_OK; +} + +static struct notifier_block powerclamp_cpu_notifier = { + .notifier_call = powerclamp_cpu_callback, +}; + +static int powerclamp_get_max_state(struct thermal_cooling_device *cdev, + unsigned long *state) +{ + *state = MAX_TARGET_RATIO; + + return 0; +} + +static int powerclamp_get_cur_state(struct thermal_cooling_device *cdev, + unsigned long *state) +{ + if (true == clamping) + *state = pkg_cstate_ratio_cur; + else + /* to save power, do not poll idle ratio while not clamping */ + *state = -1; /* indicates invalid state */ + + return 0; +} + +static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev, + unsigned long new_target_ratio) +{ + int ret = 0; + + new_target_ratio = clamp(new_target_ratio, 0UL, + (unsigned long) (MAX_TARGET_RATIO-1)); + if (set_target_ratio == 0 && new_target_ratio > 0) { + pr_info("Start idle injection to reduce power\n"); + set_target_ratio = new_target_ratio; + ret = start_power_clamp(); + goto exit_set; + } else if (set_target_ratio > 0 && new_target_ratio == 0) { + pr_info("Stop forced idle injection\n"); + set_target_ratio = 0; + end_power_clamp(); + } else /* adjust currently running */ { + set_target_ratio = new_target_ratio; + /* make new set_target_ratio visible to other cpus */ + smp_mb(); + } + +exit_set: + return ret; +} + +/* bind to generic thermal layer as cooling device*/ +static struct thermal_cooling_device_ops powerclamp_cooling_ops = { + .get_max_state = powerclamp_get_max_state, + .get_cur_state = powerclamp_get_cur_state, + .set_cur_state = powerclamp_set_cur_state, +}; + +/* runs on Nehalem and later */ +static const struct x86_cpu_id intel_powerclamp_ids[] = { + { X86_VENDOR_INTEL, 6, 0x1a}, + { X86_VENDOR_INTEL, 6, 0x1c}, + { X86_VENDOR_INTEL, 6, 0x1e}, + { X86_VENDOR_INTEL, 6, 0x1f}, + { X86_VENDOR_INTEL, 6, 0x25}, + { X86_VENDOR_INTEL, 6, 0x26}, + { X86_VENDOR_INTEL, 6, 0x2a}, + { X86_VENDOR_INTEL, 6, 0x2c}, + { X86_VENDOR_INTEL, 6, 0x2d}, + { X86_VENDOR_INTEL, 6, 0x2e}, + { X86_VENDOR_INTEL, 6, 0x2f}, + { X86_VENDOR_INTEL, 6, 0x3a}, + {} +}; +MODULE_DEVICE_TABLE(x86cpu, intel_powerclamp_ids); + +static int powerclamp_probe(void) +{ + if (!x86_match_cpu(intel_powerclamp_ids)) { + pr_err("Intel powerclamp does not run on family %d model %d\n", + boot_cpu_data.x86, boot_cpu_data.x86_model); + return -ENODEV; + } + if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC) || + !boot_cpu_has(X86_FEATURE_CONSTANT_TSC) || + !boot_cpu_has(X86_FEATURE_MWAIT) || + !boot_cpu_has(X86_FEATURE_ARAT)) + return -ENODEV; + + /* find the deepest mwait value */ + find_target_mwait(); + + return 0; +} + +static int powerclamp_debug_show(struct seq_file *m, void *unused) +{ + int i = 0; + + seq_printf(m, "controlling cpu: %d\n", control_cpu); + seq_printf(m, "pct confidence steady dynamic (compensation)\n"); + for (i = 0; i < MAX_TARGET_RATIO; i++) { + seq_printf(m, "%d\t%lu\t%lu\t%lu\n", + i, + cal_data[i].confidence, + cal_data[i].steady_comp, + cal_data[i].dynamic_comp); + } + + return 0; +} + +static int powerclamp_debug_open(struct inode *inode, + struct file *file) +{ + return single_open(file, powerclamp_debug_show, inode->i_private); +} + +static const struct file_operations powerclamp_debug_fops = { + .open = powerclamp_debug_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, + .owner = THIS_MODULE, +}; + +static inline void powerclamp_create_debug_files(void) +{ + debug_dir = debugfs_create_dir("intel_powerclamp", NULL); + if (!debug_dir) + return; + + if (!debugfs_create_file("powerclamp_calib", S_IRUGO, debug_dir, + cal_data, &powerclamp_debug_fops)) + goto file_error; + + return; + +file_error: + debugfs_remove_recursive(debug_dir); +} + +static int powerclamp_init(void) +{ + int retval; + int bitmap_size; + + bitmap_size = BITS_TO_LONGS(num_possible_cpus()) * sizeof(long); + cpu_clamping_mask = kzalloc(bitmap_size, GFP_KERNEL); + if (!cpu_clamping_mask) + return -ENOMEM; + + /* probe cpu features and ids here */ + retval = powerclamp_probe(); + if (retval) + return retval; + /* set default limit, maybe adjusted during runtime based on feedback */ + window_size = 2; + register_hotcpu_notifier(&powerclamp_cpu_notifier); + powerclamp_thread = alloc_percpu(struct task_struct *); + cooling_dev = thermal_cooling_device_register("intel_powerclamp", NULL, + &powerclamp_cooling_ops); + if (IS_ERR(cooling_dev)) + return -ENODEV; + + if (!duration) + duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES); + powerclamp_create_debug_files(); + + return 0; +} +module_init(powerclamp_init); + +static void powerclamp_exit(void) +{ + unregister_hotcpu_notifier(&powerclamp_cpu_notifier); + end_power_clamp(); + free_percpu(powerclamp_thread); + thermal_cooling_device_unregister(cooling_dev); + kfree(cpu_clamping_mask); + + cancel_delayed_work_sync(&poll_pkg_cstate_work); + debugfs_remove_recursive(debug_dir); +} +module_exit(powerclamp_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>"); +MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>"); +MODULE_DESCRIPTION("Package Level C-state Idle Injection for Intel CPUs");