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Message-ID: <1594304.lVcRDcB3yL@vostro.rjw.lan> Date: Wed, 07 Oct 2015 01:06:17 +0200 From: "Rafael J. Wysocki" <rjw@...ysocki.net> To: Prarit Bhargava <prarit@...hat.com> Cc: Kristen Carlson Accardi <kristen@...ux.intel.com>, linux-kernel@...r.kernel.org, Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org Subject: Re: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct on governor switch On Wednesday, October 07, 2015 12:43:55 AM Rafael J. Wysocki wrote: > On Tuesday, October 06, 2015 05:49:07 PM Prarit Bhargava wrote: > > Intel CPUs will not enter higher p-states when after switching from the > > performance governor to the powersave governor, until > > /sys/devices/system/cpu/intel_pstate/min_perf_pct is set to a low value. > > This differs from previous behaviour in which a switch to the powersave > > governor would result in a low default value for min_perf_pct. > > > > The behavior of the powersave governor changed after commit a04759924e25 > > ("[cpufreq] intel_pstate: honor user space min_perf_pct override on > > resume"). The commit introduced tracking of performance percentage > > changes via sysfs in order to restore userspace changes during > > suspend/resume. The problem occurs because the global values of the newly > > introduced max_sysfs_pct and min_sysfs_pct are not reset on a governor > > change and this causes the new governor to inherit the previous governor's > > settings. > > > > This patch sets max_sysfs_pct to 100 and min_sysfs_pct to 0 on a governor > > change which fixes the problem with governor switching. These changes > > also make the initial calculations for max_perf_pct and min_perf_pct > > slightly simpler. > > > > Before patch: > > [root@...el-skylake-y-01 power]# cpupower frequency-set -g performance > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct > > 100 > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct > > 100 > > [root@...el-skylake-y-01 power]# cpupower frequency-set -g powersave > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct > > 100 > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct > > 100 > > > > After patch: > > [root@...el-skylake-y-01 power]# cpupower frequency-set -g performance > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct > > 100 > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct > > 100 > > [root@...el-skylake-y-01 power]# cpupower frequency-set -g powersave > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/min_perf_pct > > 14 > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/max_perf_pct > > 100 > > > > Also note that I have tested suspend/resume (using CONFIG_PM_DEBUG): > > [root@...el-skylake-y-01 power]# echo 50 > /sys/devices/system/cpu/intel_pstate/min_perf_pct > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/*_perf_pct > > 100 > > 50 > > [root@...el-skylake-y-01 power]# echo devices > /sys/power/pm_test > > [root@...el-skylake-y-01 power]# echo platform > /sys/power/disk > > [root@...el-skylake-y-01 power]# echo disk > /sys/power/state > > [root@...el-skylake-y-01 power]# cat /sys/devices/system/cpu/intel_pstate/*_perf_pct > > 100 > > 50 > > > > Fixes: a04759924e25 ("[cpufreq] intel_pstate: honor user space min_perf_pct override on resume") > > Cc: Kristen Carlson Accardi <kristen@...ux.intel.com> > > Cc: "Rafael J. Wysocki" <rjw@...ysocki.net> > > Cc: Viresh Kumar <viresh.kumar@...aro.org> > > Cc: linux-pm@...r.kernel.org > > Signed-off-by: Prarit Bhargava <prarit@...hat.com> > > --- > > drivers/cpufreq/intel_pstate.c | 7 +++++-- > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > > index 3af9dd7..bb24458 100644 > > --- a/drivers/cpufreq/intel_pstate.c > > +++ b/drivers/cpufreq/intel_pstate.c > > @@ -986,6 +986,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) > > if (!policy->cpuinfo.max_freq) > > return -ENODEV; > > > > + limits.min_sysfs_pct = 0; > > + limits.max_sysfs_pct = 100; > > + > > if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && > > policy->max >= policy->cpuinfo.max_freq) { > > limits.min_policy_pct = 100; > > @@ -1004,9 +1007,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) > > limits.max_policy_pct = clamp_t(int, limits.max_policy_pct, 0 , 100); > > > > /* Normalize user input to [min_policy_pct, max_policy_pct] */ > > - limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct); > > + limits.min_perf_pct = limits.min_policy_pct; > > limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct); > > - limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct); > > + limits.max_perf_pct = limits.max_sysfs_pct; On a second thought, isn't that always 100? If so, doesn't it basically discard limits.max_policy_pct? > > limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct); > > > > /* Make sure min_perf_pct <= max_perf_pct */ > > Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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