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>
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 4acb904..cb560749 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -884,7 +884,7 @@
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 @@
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 @@
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 @@
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);
}
}