From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philippe Longepe Subject: [PATCH 2/3] cpufreq: intel_pstate: account for non C0 time Date: Fri, 4 Dec 2015 17:40:33 +0100 Message-ID: <1449247235-29389-6-git-send-email-philippe.longepe@linux.intel.com> References: <1449247235-29389-1-git-send-email-philippe.longepe@linux.intel.com> Return-path: Received: from mga02.intel.com ([134.134.136.20]:59932 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754052AbbLDQkt (ORCPT ); Fri, 4 Dec 2015 11:40:49 -0500 In-Reply-To: <1449247235-29389-1-git-send-email-philippe.longepe@linux.intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: linux-pm@vger.kernel.org Cc: srinivas.pandruvada@linux.intel.com, Philippe Longepe , Stephane Gasparini From: Philippe Longepe The current function to calculate cpu utilization uses the average P-state ratio (APerf/Mperf) scaled by the ratio of the current P-state to the max available non-turbo one. This leads to an overestimation of utilization which causes higher-performance P-states to be selected more often and that leads to increased energy consumption. This is a problem for low-power systems, so it is better to use a different utilization calculation algorithm for them. Namely, the Percent Busy value (or load) can be estimated as the ratio of the MPERF counter that runs at a constant rate only during active periods (C0) to the time stamp counter (TSC) that also runs (at the same rate) during idle. That is: Percent Busy = 100 * (delta_mperf / delta_tsc) Use this algorithm for platforms with SoCs based on the Airmont and Silvermont Atom cores. Signed-off-by: Philippe Longepe Signed-off-by: Stephane Gasparini --- drivers/cpufreq/intel_pstate.c | 29 ++++++++++++++++++++++++----- 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 6a301e1..c8437861 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -143,6 +143,7 @@ struct cpu_defaults { }; static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu); +static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu); static struct pstate_adjust_policy pid_params; static struct pstate_funcs pstate_funcs; @@ -763,7 +764,7 @@ static struct cpu_defaults silvermont_params = { .set = atom_set_pstate, .get_scaling = silvermont_get_scaling, .get_vid = atom_get_vid, - .get_target_pstate = get_target_pstate_use_performance, + .get_target_pstate = get_target_pstate_use_cpu_load, }, }; @@ -784,7 +785,7 @@ static struct cpu_defaults airmont_params = { .set = atom_set_pstate, .get_scaling = airmont_get_scaling, .get_vid = atom_get_vid, - .get_target_pstate = get_target_pstate_use_performance, + .get_target_pstate = get_target_pstate_use_cpu_load, }, }; @@ -890,12 +891,11 @@ static inline void intel_pstate_sample(struct cpudata *cpu) local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); - if (cpu->prev_mperf == mperf) { + tsc = rdtsc(); + if ((cpu->prev_mperf == mperf) || (cpu->prev_tsc == tsc)) { local_irq_restore(flags); return; } - - tsc = rdtsc(); local_irq_restore(flags); cpu->last_sample_time = cpu->sample.time; @@ -930,6 +930,25 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu) mod_timer_pinned(&cpu->timer, jiffies + delay); } +static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu) +{ + struct sample *sample = &cpu->sample; + int32_t cpu_load; + + /* + * The load can be estimated as the ratio of the mperf counter + * running at a constant frequency during active periods + * (C0) and the time stamp counter running at the same frequency + * also during C-states. + */ + cpu_load = div64_u64(int_tofp(100) * sample->mperf, sample->tsc); + + cpu->sample.busy_scaled = cpu_load; + + return cpu->pstate.current_pstate - pid_calc(&cpu->pid, cpu_load); +} + + static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu) { int32_t core_busy, max_pstate, current_pstate, sample_ratio; -- 1.9.1