On Wed, Mar 1, 2017 at 12:09 AM, Rafael J. Wysocki <r...@rjwysocki.net> wrote: > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > If the current P-state selection algorithm is set to "performance" > in intel_pstate_set_policy(), the limits may be initialized from > scratch, but only if no_turbo is not set and the maximum frequency > allowed for the given CPU (i.e. the policy object representing it) > is at least equal to the max frequency supported by the CPU. In all > of the other cases, the limits will not be updated. > > For example, the following can happen: > > # cat intel_pstate/status > active > # echo performance > cpufreq/policy0/scaling_governor > # cat intel_pstate/min_perf_pct > 100 > # echo 94 > intel_pstate/min_perf_pct > # cat intel_pstate/min_perf_pct > 100 > # cat cpufreq/policy0/scaling_max_freq > 3100000 > echo 3000000 > cpufreq/policy0/scaling_max_freq > # cat intel_pstate/min_perf_pct > 94 > # echo 95 > intel_pstate/min_perf_pct > # cat intel_pstate/min_perf_pct > 95 > > That is confusing for two reasons. First, the initial attempt to > change min_perf_pct to 94 seems to have no effect, even though > setting the global limits should always work. Second, after > changing scaling_max_freq for policy0 the global min_perf_pct > attribute shows 94, even though it should have not been affected > by that operation in principle. > > Moreover, the final attempt to change min_perf_pct to 95 worked > as expected, because scaling_max_freq for the only policy with > scaling_governor equal to "performance" was different from the > maximum at that time. > > To make all that confusion go away, modify intel_pstate_set_policy() > so that it doesn't reinitialize the limits at all. > > At the same time, change intel_pstate_set_performance_limits() to > set min_sysfs_pct to 100 in the "performance" limits set so that > switching the P-state selection algorithm to "performance" causes > intel_pstate/min_perf_pct in sysfs to go to 100 (or whatever value > min_sysfs_pct in the "performance" limits is set to later). > > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > --- > > -> v2: No changes > > --- > drivers/cpufreq/intel_pstate.c | 10 +++------- > 1 file changed, 3 insertions(+), 7 deletions(-) > > Index: linux-pm/drivers/cpufreq/intel_pstate.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c > +++ linux-pm/drivers/cpufreq/intel_pstate.c > @@ -382,6 +382,7 @@ static void intel_pstate_set_performance > intel_pstate_init_limits(limits); > limits->min_perf_pct = 100; > limits->min_perf = int_ext_tofp(1); > + limits->min_sysfs_pct = 100;
This change breaks the per-CPU limits, so the patch is not correct. Withdrawing. Thanks, Rafael
