lkml.org 
[lkml]   [2011]   [Jun]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
DateWed, 15 Jun 2011 17:28:35 -0700
FromGreg KH <>
Subject[39/85] cpuidle: menu: fixed wrapping timers at 4.294 seconds
2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------
From: Tero Kristo <tero.kristo@nokia.com>

commit 7467571f4480b273007517b26297c07154c73924 upstream.

Cpuidle menu governor is using u32 as a temporary datatype for storing
nanosecond values which wrap around at 4.294 seconds. This causes errors
in predicted sleep times resulting in higher than should be C state
selection and increased power consumption. This also breaks cpuidle
state residency statistics.

Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/cpuidle/governors/menu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -185,6 +185,7 @@ static int menu_select(struct cpuidle_de
int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
int i;
int multiplier;
+ struct timespec t;

if (data->needs_update) {
menu_update(dev);
@@ -199,8 +200,9 @@ static int menu_select(struct cpuidle_de
return 0;

/* determine the expected residency time, round up */
+ t = ktime_to_timespec(tick_nohz_get_sleep_length());
data->expected_us =
- DIV_ROUND_UP((u32)ktime_to_ns(tick_nohz_get_sleep_length()), 1000);
+ t.tv_sec * USEC_PER_SEC + t.tv_nsec / NSEC_PER_USEC;


data->bucket = which_bucket(data->expected_us);



\
 
 \ /
  Last update: 2011-06-16 09:15    [from the cache]
©2003-2010