Messages in this thread | | | Date | Fri, 20 Nov 2015 10:10:00 -0500 | From | Prarit Bhargava <> | Subject | Re: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error |
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On 11/20/2015 08:18 AM, Viresh Kumar wrote: > On 20-11-15, 07:32, Prarit Bhargava wrote: >> I have a Intel (6,63) processor with a "marketing" frequency (from >> /proc/cpuinfo) of 2100MHz, and a max turbo frequency of 2600MHz. I >> can execute >> >> cpupower frequency-set -g powersave --min 1200MHz --max 2100MHz >> >> and the max_freq_pct is set to 80. When adding load to the system I noticed >> that the cpu frequency only reached 2000MHZ and not 2100MHz as expected. >> >> This is because limits->max_policy_pct is calculated as 2100 * 100 /2600 = 80.7 >> and is rounded down to 80 when it should be rounded up to 81. This patch >> adds a DIV_ROUND_UP() which will return the correct value. >> >> Cc: Srinivas Pandruvada <srinivas.pandruvada@intel.com> >> Cc: Len Brown <len.brown@intel.com> >> Cc: Alexandra Yates <alexandra.yates@intel.com> >> Cc: Kristen Carlson Accardi <kristen@linux.intel.com> >> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> >> Cc: Viresh Kumar <viresh.kumar@linaro.org> >> Cc: linux-pm@vger.kernel.org >> Signed-off-by: Prarit Bhargava <prarit@redhat.com> >> --- >> drivers/cpufreq/intel_pstate.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c >> index 001a532..6b63374 100644 >> --- a/drivers/cpufreq/intel_pstate.c >> +++ b/drivers/cpufreq/intel_pstate.c >> @@ -1110,6 +1110,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) >> limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, 0 , 100); >> limits->max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq; > > Forgot to remove this line ? > >> limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100); > > And put this after the later one ? > >> + limits->max_policy_pct = DIV_ROUND_UP(policy->max * 100, >> + policy->cpuinfo.max_freq); >> >> /* Normalize user input to [min_policy_pct, max_policy_pct] */ >> limits->min_perf_pct = max(limits->min_policy_pct, > > Sure you tested it ? :)
Oops -- and yeah, tested. It works because I rewrite the value of max_policy_pct :). I'll repost shortly.
P.
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