| Message ID | 12460110.O9o76ZdvQC@rjwysocki.net (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | [v1] cpufreq: intel_pstate: Use HWP to initialize ITMT if CPPC is missing | expand |
On 6/20/2024 11:14, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > It is reported that single-thread performance on some hybrid systems > dropped significantly after commit 7feec7430edd ("ACPI: CPPC: Only probe > for _CPC if CPPC v2 is acked") which prevented _CPC from being used if > the support for it had not been confirmed by the platform firmware. > > The problem is that if the platform firmware does not confirm CPPC v2 > support, cppc_get_perf_caps() returns an error which prevents the > intel_pstate driver from enabling ITMT. Consequently, the scheduler > does not get any hints on CPU performance differences, so in a hybrid > system some tasks may run on CPUs with lower capacity even though they > should be running on high-capacity CPUs. > > To address this, modify intel_pstate to use the information from > MSR_HWP_CAPABILITIES to enable ITMT if CPPC is not available (which is > done already if the highest performance number coming from CPPC is not > realistic). > > Fixes: 7feec7430edd ("ACPI: CPPC: Only probe for _CPC if CPPC v2 is acked") > Closes: https://lore.kernel.org/linux-acpi/d01b0a1f-bd33-47fe-ab41-43843d8a374f@kfocus.org > Link: https://lore.kernel.org/linux-acpi/ZnD22b3Br1ng7alf@kf-XE > Reported-by: Aaron Rainbolt <arainbolt@kfocus.org> > Tested-by: Aaron Rainbolt <arainbolt@kfocus.org> > Cc: 5.19+ <stable@vger.kernel.org> # 5.19+ > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> > --- > drivers/cpufreq/intel_pstate.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > Index: linux-pm/drivers/cpufreq/intel_pstate.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c > +++ linux-pm/drivers/cpufreq/intel_pstate.c > @@ -355,15 +355,14 @@ static void intel_pstate_set_itmt_prio(i > int ret; > > ret = cppc_get_perf_caps(cpu, &cppc_perf); > - if (ret) > - return; > - > /* > - * On some systems with overclocking enabled, CPPC.highest_perf is hardcoded to 0xff. > - * In this case we can't use CPPC.highest_perf to enable ITMT. > - * In this case we can look at MSR_HWP_CAPABILITIES bits [8:0] to decide. > + * If CPPC is not available, fall back to MSR_HWP_CAPABILITIES bits [8:0]. > + * > + * Also, on some systems with overclocking enabled, CPPC.highest_perf is > + * hardcoded to 0xff, so CPPC.highest_perf cannot be used to enable ITMT. > + * Fall back to MSR_HWP_CAPABILITIES then too. > */ > - if (cppc_perf.highest_perf == CPPC_MAX_PERF) > + if (ret || cppc_perf.highest_perf == CPPC_MAX_PERF) > cppc_perf.highest_perf = HWP_HIGHEST_PERF(READ_ONCE(all_cpu_data[cpu]->hwp_cap_cached)); > > /* > > >
Index: linux-pm/drivers/cpufreq/intel_pstate.c =================================================================== --- linux-pm.orig/drivers/cpufreq/intel_pstate.c +++ linux-pm/drivers/cpufreq/intel_pstate.c @@ -355,15 +355,14 @@ static void intel_pstate_set_itmt_prio(i int ret; ret = cppc_get_perf_caps(cpu, &cppc_perf); - if (ret) - return; - /* - * On some systems with overclocking enabled, CPPC.highest_perf is hardcoded to 0xff. - * In this case we can't use CPPC.highest_perf to enable ITMT. - * In this case we can look at MSR_HWP_CAPABILITIES bits [8:0] to decide. + * If CPPC is not available, fall back to MSR_HWP_CAPABILITIES bits [8:0]. + * + * Also, on some systems with overclocking enabled, CPPC.highest_perf is + * hardcoded to 0xff, so CPPC.highest_perf cannot be used to enable ITMT. + * Fall back to MSR_HWP_CAPABILITIES then too. */ - if (cppc_perf.highest_perf == CPPC_MAX_PERF) + if (ret || cppc_perf.highest_perf == CPPC_MAX_PERF) cppc_perf.highest_perf = HWP_HIGHEST_PERF(READ_ONCE(all_cpu_data[cpu]->hwp_cap_cached)); /*