* [PATCH] intel_pstate: Do not skip samples partially
@ 2016-03-10 22:45 Rafael J. Wysocki
2016-03-10 22:53 ` Srinivas Pandruvada
0 siblings, 1 reply; 2+ messages in thread
From: Rafael J. Wysocki @ 2016-03-10 22:45 UTC (permalink / raw)
To: Srinivas Pandruvada, Linux PM list
Cc: Linux Kernel Mailing List, Philippe Longepe
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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>
---
On top of my linux-next branch.
---
drivers/cpufreq/intel_pstate.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -890,7 +890,7 @@ static inline void intel_pstate_calc_bus
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;
@@ -900,9 +900,9 @@ static inline void intel_pstate_sample(s
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);
@@ -920,6 +920,7 @@ static inline void intel_pstate_sample(s
cpu->prev_aperf = aperf;
cpu->prev_mperf = mperf;
cpu->prev_tsc = tsc;
+ return true;
}
static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu)
@@ -1026,8 +1027,9 @@ static void intel_pstate_update_util(str
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);
}
}
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] intel_pstate: Do not skip samples partially
2016-03-10 22:45 [PATCH] intel_pstate: Do not skip samples partially Rafael J. Wysocki
@ 2016-03-10 22:53 ` Srinivas Pandruvada
0 siblings, 0 replies; 2+ messages in thread
From: Srinivas Pandruvada @ 2016-03-10 22:53 UTC (permalink / raw)
To: Rafael J. Wysocki, Linux PM list
Cc: Linux Kernel Mailing List, Philippe Longepe
On Thu, 2016-03-10 at 23:45 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> 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>
> ---
>
> On top of my linux-next branch.
>
> ---
> drivers/cpufreq/intel_pstate.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> Index: linux-pm/drivers/cpufreq/intel_pstate.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> +++ linux-pm/drivers/cpufreq/intel_pstate.c
> @@ -890,7 +890,7 @@ static inline void intel_pstate_calc_bus
> 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;
> @@ -900,9 +900,9 @@ static inline void intel_pstate_sample(s
> 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);
>
> @@ -920,6 +920,7 @@ static inline void intel_pstate_sample(s
> cpu->prev_aperf = aperf;
> cpu->prev_mperf = mperf;
> cpu->prev_tsc = tsc;
> + return true;
> }
>
> static inline int32_t get_target_pstate_use_cpu_load(struct cpudata
> *cpu)
> @@ -1026,8 +1027,9 @@ static void intel_pstate_update_util(str
> 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);
> }
> }
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm"
> in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 2+ messages in thread
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