@@ -17,6 +17,7 @@
#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/percpu.h>
+#include <linux/sched/isolation.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
@@ -88,18 +89,28 @@ int __init parse_acpi_topology(void)
* initialized.
*/
static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = 1UL << (2 * SCHED_CAPACITY_SHIFT);
-static DEFINE_PER_CPU(u64, arch_const_cycles_prev);
-static DEFINE_PER_CPU(u64, arch_core_cycles_prev);
static cpumask_var_t amu_fie_cpus;
+struct amu_cntr_sample {
+ u64 arch_const_cycles_prev;
+ u64 arch_core_cycles_prev;
+ unsigned long last_update;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct amu_cntr_sample, cpu_amu_samples);
+
void update_freq_counters_refs(void)
{
- this_cpu_write(arch_core_cycles_prev, read_corecnt());
- this_cpu_write(arch_const_cycles_prev, read_constcnt());
+ struct amu_cntr_sample *amu_sample = this_cpu_ptr(&cpu_amu_samples);
+
+ amu_sample->arch_core_cycles_prev = read_corecnt();
+ amu_sample->arch_const_cycles_prev = read_constcnt();
}
static inline bool freq_counters_valid(int cpu)
{
+ struct amu_cntr_sample *amu_sample = per_cpu_ptr(&cpu_amu_samples, cpu);
+
if ((cpu >= nr_cpu_ids) || !cpumask_test_cpu(cpu, cpu_present_mask))
return false;
@@ -108,8 +119,8 @@ static inline bool freq_counters_valid(int cpu)
return false;
}
- if (unlikely(!per_cpu(arch_const_cycles_prev, cpu) ||
- !per_cpu(arch_core_cycles_prev, cpu))) {
+ if (unlikely(!amu_sample->arch_const_cycles_prev ||
+ !amu_sample->arch_core_cycles_prev)) {
pr_debug("CPU%d: cycle counters are not enabled.\n", cpu);
return false;
}
@@ -152,17 +163,22 @@ void freq_inv_set_max_ratio(int cpu, u64 max_rate)
static void amu_scale_freq_tick(void)
{
+ struct amu_cntr_sample *amu_sample = this_cpu_ptr(&cpu_amu_samples);
u64 prev_core_cnt, prev_const_cnt;
u64 core_cnt, const_cnt, scale;
- prev_const_cnt = this_cpu_read(arch_const_cycles_prev);
- prev_core_cnt = this_cpu_read(arch_core_cycles_prev);
+ prev_const_cnt = amu_sample->arch_const_cycles_prev;
+ prev_core_cnt = amu_sample->arch_core_cycles_prev;
update_freq_counters_refs();
- const_cnt = this_cpu_read(arch_const_cycles_prev);
- core_cnt = this_cpu_read(arch_core_cycles_prev);
+ const_cnt = amu_sample->arch_const_cycles_prev;
+ core_cnt = amu_sample->arch_core_cycles_prev;
+ /*
+ * This should not happen unless the AMUs have been reset and the
+ * counter values have not been restored - unlikely
+ */
if (unlikely(core_cnt <= prev_core_cnt ||
const_cnt <= prev_const_cnt))
return;
@@ -182,6 +198,8 @@ static void amu_scale_freq_tick(void)
scale = min_t(unsigned long, scale, SCHED_CAPACITY_SCALE);
this_cpu_write(arch_freq_scale, (unsigned long)scale);
+
+ amu_sample->last_update = jiffies;
}
static struct scale_freq_data amu_sfd = {
@@ -189,6 +207,80 @@ static struct scale_freq_data amu_sfd = {
.set_freq_scale = amu_scale_freq_tick,
};
+#define AMU_SAMPLE_EXP_MS 20
+
+unsigned int arch_freq_get_on_cpu(int cpu)
+{
+ struct amu_cntr_sample *amu_sample;
+ cpumask_var_t ref_cpumask = NULL;
+ unsigned long last_update;
+ unsigned int freq;
+ u64 scale;
+
+ if (!cpumask_test_cpu(cpu, amu_fie_cpus) || !arch_scale_freq_ref(cpu))
+ return 0;
+retry:
+ amu_sample = per_cpu_ptr(&cpu_amu_samples, cpu);
+
+ last_update = amu_sample->last_update;
+
+ /*
+ * For those CPUs that are in full dynticks mode,
+ * and those that have not seen tick for a while
+ * try an alternative source for the counters (and thus freq scale),
+ * if available, for given policy:
+ * this boils down to identifying an active cpu within the same freq
+ * domain, if any.
+ */
+ if (!housekeeping_cpu(cpu, HK_TYPE_TICK) ||
+ time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
+ struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+ int ref_cpu = cpu;
+
+ if (!policy_is_shared(policy)) {
+ cpufreq_cpu_put(policy);
+ return 0;
+ }
+
+ if (!ref_cpumask) {
+ if (!zalloc_cpumask_var(&ref_cpumask, GFP_KERNEL)) {
+ cpufreq_cpu_put(policy);
+ return 0;
+ }
+
+ cpumask_copy(ref_cpumask, policy->cpus);
+ }
+
+ cpufreq_cpu_put(policy);
+
+ do {
+ cpumask_clear_cpu(ref_cpu, ref_cpumask);
+ ref_cpu = cpumask_first(ref_cpumask);
+
+ } while (ref_cpu < nr_cpu_ids && idle_cpu(ref_cpu));
+
+ if (ref_cpu >= nr_cpu_ids) {
+ /* No alternative to pull info from */
+ free_cpumask_var(ref_cpumask);
+ return 0;
+ }
+ cpu = ref_cpu;
+ goto retry;
+ }
+ /*
+ * Reversed computation to the one used to determine
+ * the arch_freq_scale value
+ * (see amu_scale_freq_tick for details)
+ */
+ scale = arch_scale_freq_capacity(cpu);
+ freq = scale * arch_scale_freq_ref(cpu);
+ freq >>= SCHED_CAPACITY_SHIFT;
+
+ free_cpumask_var(ref_cpumask);
+
+ return freq;
+}
+
static void amu_fie_setup(const struct cpumask *cpus)
{
int cpu;
With the Frequency Invariance Engine (FIE) being already wired up with sched tick and making use of relevant (core counter and constant counter) AMU counters, getting the current frequency for a given CPU, can be achieved by utilizing the frequency scale factor which reflects an average CPU frequency for the last tick period length. The solution is partially based on APERF/MPERF implementation of arch_freq_get_on_cpu. Suggested-by: Ionela Voinescu <ionela.voinescu@arm.com> Signed-off-by: Beata Michalska <beata.michalska@arm.com> --- arch/arm64/kernel/topology.c | 112 +++++++++++++++++++++++++++++++---- 1 file changed, 102 insertions(+), 10 deletions(-)