2011-02-24 14:18:15

by Tero Kristo

Subject: [PATCH] cpuidle: menu: fixed wrapping timers at 4.294 seconds

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 <[email protected]>
---
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);
--
1.7.1

2011-04-02 00:07:26

by Len Brown

Subject: Re: [PATCH] cpuidle: menu: fixed wrapping timers at 4.294 seconds

applied to idle-test

thanks,
Len Brown, Intel Open Source Technology Center

ps. please cc linux-pm on cpuidle pathces

On Thu, 24 Feb 2011, Tero Kristo wrote:

> 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 <[email protected]>
> ---
> 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);
> --
> 1.7.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>