From: Prarit Bhargava <prarit@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Prarit Bhargava <prarit@redhat.com>,
Srinivas Pandruvada <srinivas.pandruvada@intel.com>,
Len Brown <len.brown@intel.com>,
Alexandra Yates <alexandra.yates@intel.com>,
Kristen Carlson Accardi <kristen@linux.intel.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Viresh Kumar <viresh.kumar@linaro.org>,
linux-pm@vger.kernel.org
Subject: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error
Date: Fri, 20 Nov 2015 07:32:36 -0500 [thread overview]
Message-ID: <1448022757-7856-2-git-send-email-prarit@redhat.com> (raw)
In-Reply-To: <1448022757-7856-1-git-send-email-prarit@redhat.com>
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
next prev parent reply other threads:[~2015-11-20 12:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-20 12:32 [PATCH 0/2 v2] cpufreq, intel_pstate, Fix rounding errors Prarit Bhargava
2015-11-20 12:32 ` Prarit Bhargava [this message]
2015-11-20 13:18 ` [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error Viresh Kumar
2015-11-20 15:10 ` Prarit Bhargava
2015-11-20 15:19 ` Viresh Kumar
2015-11-20 15:43 ` Prarit Bhargava
2015-11-20 20:02 ` Pandruvada, Srinivas
2015-11-20 23:47 ` Prarit Bhargava
2015-11-20 23:57 ` Pandruvada, Srinivas
2015-11-20 12:32 ` [PATCH 2/2] cpufreq, intel_pstate, fix limits->max_perf " Prarit Bhargava
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