On Thu, Mar 2, 2017 at 6:18 PM, Rafael J. Wysocki <raf...@kernel.org> wrote: > 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.
Actually, it appears to be fixable, so I will send a new version later, most likely. Thanks, Rafael
