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intel_pstate: Clean up get_target_pstate_use_performance()

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The comments and the core_busy variable name in
get_target_pstate_use_performance() are totally confusing,
so modify them to reflect what's going on.

The results of the computations should be the same as before.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2016-05-11 19:11:26 +02:00
parent 8edb0a6e48
commit 1aa7a6e2b8
1 changed files with 11 additions and 16 deletions
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27
drivers/cpufreq/intel_pstate.c
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@ -1259,43 +1259,38 @@ static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu)
static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu)
{
int32_t core_busy, max_pstate, current_pstate, sample_ratio;
int32_t perf_scaled, max_pstate, current_pstate, sample_ratio;
u64 duration_ns;
/*
* core_busy is the ratio of actual performance to max
* max_pstate is the max non turbo pstate available
* current_pstate was the pstate that was requested during
* the last sample period.
*
* We normalize core_busy, which was our actual percent
* performance to what we requested during the last sample
* period. The result will be a percentage of busy at a
* specified pstate.
* perf_scaled is the average performance during the last sampling
* period scaled by the ratio of the maximum P-state to the P-state
* requested last time (in percent). That measures the system's
* response to the previous P-state selection.
*/
max_pstate = cpu->pstate.max_pstate_physical;
current_pstate = cpu->pstate.current_pstate;
core_busy = mul_ext_fp(cpu->sample.core_avg_perf,
perf_scaled = mul_ext_fp(cpu->sample.core_avg_perf,
div_fp(100 * max_pstate, current_pstate));
/*
* Since our utilization update callback will not run unless we are
* in C0, check if the actual elapsed time is significantly greater (3x)
* than our sample interval. If it is, then we were idle for a long
* enough period of time to adjust our busyness.
* enough period of time to adjust our performance metric.
*/
duration_ns = cpu->sample.time - cpu->last_sample_time;
if ((s64)duration_ns > pid_params.sample_rate_ns * 3) {
sample_ratio = div_fp(pid_params.sample_rate_ns, duration_ns);
core_busy = mul_fp(core_busy, sample_ratio);
perf_scaled = mul_fp(perf_scaled, sample_ratio);
} else {
sample_ratio = div_fp(100 * cpu->sample.mperf, cpu->sample.tsc);
if (sample_ratio < int_tofp(1))
core_busy = 0;
perf_scaled = 0;
}
cpu->sample.busy_scaled = core_busy;
return cpu->pstate.current_pstate - pid_calc(&cpu->pid, core_busy);
cpu->sample.busy_scaled = perf_scaled;
return cpu->pstate.current_pstate - pid_calc(&cpu->pid, perf_scaled);
}
static inline void intel_pstate_update_pstate(struct cpudata *cpu, int pstate)