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| author | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-10-06 14:07:51 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-10-12 20:58:13 +0200 |
| commit | 0843e83c1a4aa67e08f424430526c948d591d5f1 (patch) | |
| tree | 3e86a9c1e9fe52ff303122874e4c3b2aff9551f3 /drivers | |
| parent | cpufreq: intel_pstate: Clarify comment in get_target_pstate_use_performance() (diff) | |
| download | linux-0843e83c1a4aa67e08f424430526c948d591d5f1.tar.xz linux-0843e83c1a4aa67e08f424430526c948d591d5f1.zip | |
cpufreq: intel_pstate: Proportional algorithm for Atom
The PID algorithm used by the intel_pstate driver tends to drive
performance to the minimum for workloads with utilization below the
setpoint, which is undesirable, so replace it with a modified
"proportional" algorithm on Atom.
The new algorithm will set the new P-state to be 1.25 times the
available maximum times the (frequency-invariant) utilization during
the previous sampling period except when the target P-state computed
this way is lower than the average P-state during the previous
sampling period. In the latter case, it will increase the target by
50% of the difference between it and the average P-state to prevent
performance from dropping down too fast in some cases.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/cpufreq/intel_pstate.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 1c7b91c5805b..6c8c897d0a2d 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1232,6 +1232,7 @@ static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu) { struct sample *sample = &cpu->sample; int32_t busy_frac, boost; + int target, avg_pstate; busy_frac = div_fp(sample->mperf, sample->tsc); @@ -1242,7 +1243,26 @@ static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu) busy_frac = boost; sample->busy_scaled = busy_frac * 100; - return get_avg_pstate(cpu) - pid_calc(&cpu->pid, sample->busy_scaled); + + target = limits->no_turbo || limits->turbo_disabled ? + cpu->pstate.max_pstate : cpu->pstate.turbo_pstate; + target += target >> 2; + target = mul_fp(target, busy_frac); + if (target < cpu->pstate.min_pstate) + target = cpu->pstate.min_pstate; + + /* + * If the average P-state during the previous cycle was higher than the + * current target, add 50% of the difference to the target to reduce + * possible performance oscillations and offset possible performance + * loss related to moving the workload from one CPU to another within + * a package/module. + */ + avg_pstate = get_avg_pstate(cpu); + if (avg_pstate > target) + target += (avg_pstate - target) >> 1; + + return target; } static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu) |