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Old 06-22-2011, 09:40 AM
Colin King
 
Default cpuidle: menu: fixed wrapping timers at 4.294 seconds

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

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.

cc: stable@kernel.org # .32.x through .39.x
Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Len Brown <len.brown@intel.com>
---
drivers/cpuidle/governors/menu.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index f508690..c47f3d0 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -237,6 +237,7 @@ static int menu_select(struct cpuidle_device *dev)
unsigned int power_usage = -1;
int i;
int multiplier;
+ struct timespec t;

if (data->needs_update) {
menu_update(dev);
@@ -251,8 +252,9 @@ static int menu_select(struct cpuidle_device *dev)
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);
--
1.7.0.4


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Old 06-22-2011, 12:41 PM
Stefan Bader
 
Default cpuidle: menu: fixed wrapping timers at 4.294 seconds

On 22.06.2011 11:40, Colin King wrote:
> From: Tero Kristo <tero.kristo@nokia.com>
>
> 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.
>
> cc: stable@kernel.org # .32.x through .39.x
> Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
> Signed-off-by: Len Brown <len.brown@intel.com>
> ---
> drivers/cpuidle/governors/menu.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index f508690..c47f3d0 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -237,6 +237,7 @@ static int menu_select(struct cpuidle_device *dev)
> unsigned int power_usage = -1;
> int i;
> int multiplier;
> + struct timespec t;
>
> if (data->needs_update) {
> menu_update(dev);
> @@ -251,8 +252,9 @@ static int menu_select(struct cpuidle_device *dev)
> 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);

Clean pick and also queued for upstream stable.

Acked-by: Stefan Bader <stefan.bader@canonical.com>

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