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From: Stratos Karafotis <stratosk@semaphore.gr>
To: rjw@rjwysocki.net, viresh.kumar@linaro.org, dirk.j.brandewie@intel.com
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] cpufreq: intel_pstate: Fix rounding of core_pct
Date: Wed, 11 Jun 2014 15:33:32 +0300	[thread overview]
Message-ID: <1402490012-19969-1-git-send-email-stratosk@semaphore.gr> (raw)

Local variable core_pct holds fixed point values.
When we round it we add "1" to core_pct. This has almost
no effect.

So, add int_toftp(1) to core_pct when rounding.

For example, in a given sample point (values taken from
tracepoint) with:
aperf = 5024
mperf = 10619

the core_pct is (before rounding):
core_pct = 12111
fp_toint(core_pct) = 47

After rounding:
core_pct = 12112
fp_toint(core_pct) = 47

After rounding with int_toftp(1):
core_pct = 12367
fp_toint(core_pct) = 48

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
---

Hi Rafael,

I'm sorry for submitting again in merge window, but
I thought that maybe we need this fix for 3.16.


 drivers/cpufreq/intel_pstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 4e7f492..dd80aa2 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -564,7 +564,7 @@ static inline void intel_pstate_calc_busy(struct cpudata *cpu)
 	core_pct = div_u64_rem(core_pct, int_tofp(sample->mperf), &rem);
 
 	if ((rem << 1) >= int_tofp(sample->mperf))
-		core_pct += 1;
+		core_pct += int_tofp(1);
 
 	sample->freq = fp_toint(
 		mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));
-- 
1.9.3


             reply	other threads:[~2014-06-11 12:33 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-11 12:33 Stratos Karafotis [this message]
2014-06-11 13:41 ` [PATCH] cpufreq: intel_pstate: Fix rounding of core_pct Doug Smythies
2014-06-11 14:08   ` Stratos Karafotis
2014-06-11 15:02     ` Doug Smythies
2014-06-11 18:28       ` Rafael J. Wysocki
2014-06-11 21:40         ` Doug Smythies
2014-06-11 21:45           ` Rafael J. Wysocki
2014-06-12  6:56             ` Doug Smythies
2014-06-11 20:20       ` Stratos Karafotis
2014-06-11 21:15         ` Doug Smythies
2014-06-12 14:35           ` Stratos Karafotis
2014-06-12 20:03             ` Rafael J. Wysocki
2014-06-13  6:49               ` Doug Smythies
2014-06-13 17:39                 ` Stratos Karafotis
2014-06-13 13:48               ` Dirk Brandewie
2014-06-13 14:36                 ` Doug Smythies
2014-06-13 16:56                 ` Stratos Karafotis
2014-06-11 14:27   ` Doug Smythies

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