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intel_pstate: Do not skip samples partially 

If the current value of MPERF or the current value of TSC is the
same as the previous one, respectively, intel_pstate_sample() bails
out early and skips the sample.

However, intel_pstate_adjust_busy_pstate() is still called in that
case which is not correct, so modify intel_pstate_sample() to
return a bool value indicating whether or not the sample has been
taken and use it to decide whether or not to call
intel_pstate_adjust_busy_pstate().

While at it, remove redundant parentheses from the MPERF/TSC
check in intel_pstate_sample().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
This commit is contained in:
Rafael J. Wysocki 2016-03-10 23:45:19 +01:00
parent 8fa520af50
commit 4fec7ad5f6
1 changed files with 7 additions and 5 deletions
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12
drivers/cpufreq/intel_pstate.c
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@ -884,7 +884,7 @@ static inline void intel_pstate_calc_busy(struct cpudata *cpu)
sample->core_pct_busy = (int32_t)core_pct;
}
static inline void intel_pstate_sample(struct cpudata *cpu, u64 time)
static inline bool intel_pstate_sample(struct cpudata *cpu, u64 time)
{
u64 aperf, mperf;
unsigned long flags;
@ -894,9 +894,9 @@ static inline void intel_pstate_sample(struct cpudata *cpu, u64 time)
rdmsrl(MSR_IA32_APERF, aperf);
rdmsrl(MSR_IA32_MPERF, mperf);
tsc = rdtsc();
if ((cpu->prev_mperf == mperf) || (cpu->prev_tsc == tsc)) {
if (cpu->prev_mperf == mperf || cpu->prev_tsc == tsc) {
local_irq_restore(flags);
return;
return false;
}
local_irq_restore(flags);
@ -912,6 +912,7 @@ static inline void intel_pstate_sample(struct cpudata *cpu, u64 time)
cpu->prev_aperf = aperf;
cpu->prev_mperf = mperf;
cpu->prev_tsc = tsc;
return true;
}
static inline int32_t get_avg_frequency(struct cpudata *cpu)
@ -1025,8 +1026,9 @@ static void intel_pstate_update_util(struct update_util_data *data, u64 time,
u64 delta_ns = time - cpu->sample.time;
if ((s64)delta_ns >= pid_params.sample_rate_ns) {
intel_pstate_sample(cpu, time);
if (!hwp_active)
bool sample_taken = intel_pstate_sample(cpu, time);
if (sample_taken && !hwp_active)
intel_pstate_adjust_busy_pstate(cpu);
}
}