Messages in this thread Patch in this message | | | From | Prarit Bhargava <> | Subject | [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error | Date | Fri, 20 Nov 2015 07:32:36 -0500 |
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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; limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100); + 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, -- 1.8.3.1
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