| Message ID | 1444937661-9519-2-git-send-email-srinivas.pandruvada@linux.intel.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On Thu, 15 Oct 2015 12:34:21 -0700 Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> wrote: > This is a workaround for KNL platform, where in some cases MPERF counter > will not have updated value before next read of MSR_IA32_MPERF. In this > case divide by zero will occur. This change ignores current sample for > busy calculation in this case. > > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> > --- > drivers/cpufreq/intel_pstate.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index 3af9dd7..aa33b92 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -776,6 +776,11 @@ static inline void intel_pstate_sample(struct cpudata *cpu) > local_irq_save(flags); > rdmsrl(MSR_IA32_APERF, aperf); > rdmsrl(MSR_IA32_MPERF, mperf); > + if (cpu->prev_mperf == mperf) { > + local_irq_restore(flags); > + return; > + } > + > tsc = rdtsc(); > local_irq_restore(flags); > Acked-by: Kristen Carlson Accardi <kristen@linux.intel.com> -- 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
On Thursday, October 15, 2015 12:34:21 PM Srinivas Pandruvada wrote: > This is a workaround for KNL platform, where in some cases MPERF counter > will not have updated value before next read of MSR_IA32_MPERF. In this > case divide by zero will occur. This change ignores current sample for > busy calculation in this case. > > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Applied. I've also marked it for 4.1.y-stable (and later). Kristen, please let me know if there are any concerns regarding this one. Thanks, Rafael -- 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
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 3af9dd7..aa33b92 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -776,6 +776,11 @@ static inline void intel_pstate_sample(struct cpudata *cpu) local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + if (cpu->prev_mperf == mperf) { + local_irq_restore(flags); + return; + } + tsc = rdtsc(); local_irq_restore(flags);
This is a workaround for KNL platform, where in some cases MPERF counter will not have updated value before next read of MSR_IA32_MPERF. In this case divide by zero will occur. This change ignores current sample for busy calculation in this case. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> --- drivers/cpufreq/intel_pstate.c | 5 +++++ 1 file changed, 5 insertions(+)