cpufreq: fix jiffies/cputime mixup in conservative/ondemand governors

Commit Message

Rafael Wysocki Nov. 23, 2012, 9:48 p.m. UTC

On Friday, October 26, 2012 11:10:10 PM Rafael J. Wysocki wrote:
> On Friday, October 26, 2012 02:26:34 PM Andreas Schwab wrote:
> > "Rafael J. Wysocki" <[e-mail]> writes:
> > 
> > > http://git.kernel.org/?p=linux/kernel/git/rafael/linux-pm.git;a=shortlog;h=refs/heads/linux-next
> > 
> > 91f347c looks good, unfortunately d7d6f64 undoes the change.
> 
> I didn't notice that, sorry.  Thanks for the heads up.

So, I'm going to apply the following patch to fix this again.

Thanks,
Rafael


---
From: Rafael J. Wysocki <[e-mail]>
Subject: cpufreq: governors: Fix jiffies/cputime mixup (revisited)

This change was made by commit 8636fd2 (cpufreq: fix jiffies/cputime
mixup in conservative/ondemand governors) before, but then it has
been reverted inadvertently by commit 4471a34 (cpufreq: governors:
remove redundant code).

The changelog of commit 8636fd2 says:

  The function get_cpu_idle_time_jiffy in both the conservative and
  ondemand governors use jiffies_to_usecs to convert a cputime value
  to usecs which gives the wrong value on architectures where cputime
  and jiffies use different units.  Only matters if NO_HZ is
  disabled, since otherwise get_cpu_idle_time_us should already
  return a valid value, and get_cpu_idle_time_jiffy isn't actually
  called.

Since now we have only one common get_cpu_idle_time_jiffy() used by
both governors in question, modify it along the lines of commit
8636fd2 to restore the correct behavior.

Signed-off-by: Rafael J. Wysocki <[e-mail]>
---
 drivers/cpufreq/cpufreq_governor.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Viresh Kumar Nov. 24, 2012, 4:28 a.m. UTC | #1

On 24 November 2012 03:18, Rafael J. Wysocki <[e-mail]> wrote:
> From: Rafael J. Wysocki <[e-mail]>
> Subject: cpufreq: governors: Fix jiffies/cputime mixup (revisited)
>
> This change was made by commit 8636fd2 (cpufreq: fix jiffies/cputime
> mixup in conservative/ondemand governors) before, but then it has
> been reverted inadvertently by commit 4471a34 (cpufreq: governors:
> remove redundant code).
>
> The changelog of commit 8636fd2 says:
>
>   The function get_cpu_idle_time_jiffy in both the conservative and
>   ondemand governors use jiffies_to_usecs to convert a cputime value
>   to usecs which gives the wrong value on architectures where cputime
>   and jiffies use different units.  Only matters if NO_HZ is
>   disabled, since otherwise get_cpu_idle_time_us should already
>   return a valid value, and get_cpu_idle_time_jiffy isn't actually
>   called.
>
> Since now we have only one common get_cpu_idle_time_jiffy() used by
> both governors in question, modify it along the lines of commit
> 8636fd2 to restore the correct behavior.
>
> Signed-off-by: Rafael J. Wysocki <[e-mail]>

Reviewed-by: Viresh Kumar <[e-mail]>
--
To unsubscribe from this list: send the line "unsubscribe linux-pm" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

Index: linux/drivers/cpufreq/cpufreq_governor.c
===================================================================
--- linux.orig/drivers/cpufreq/cpufreq_governor.c
+++ linux/drivers/cpufreq/cpufreq_governor.c
@@ -45,9 +45,9 @@  static inline u64 get_cpu_idle_time_jiff
 
 	idle_time = cur_wall_time - busy_time;
 	if (wall)
-		*wall = jiffies_to_usecs(cur_wall_time);
+		*wall = cputime_to_usecs(cur_wall_time);
 
-	return jiffies_to_usecs(idle_time);
+	return cputime_to_usecs(idle_time);
 }
 
 u64 get_cpu_idle_time(unsigned int cpu, u64 *wall)