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SubjectRe: [PATCH v2 2/2] ksm: Provide support to use deferrable timers for scanner thread
On 07/31/2014 03:17 AM, Andrew Morton wrote:
> On Fri, 25 Jul 2014 20:18:18 +0530 Chintan Pandya<cpandya@codeaurora.org> wrote:
>
>> KSM thread to scan pages is scheduled on definite timeout. That wakes
>> up CPU from idle state and hence may affect the power consumption.
>> Provide an optional support to use deferrable timer which suites
>> low-power use-cases.
>>
>> Typically, on our setup we observed, 10% less power consumption with
>> some use-cases in which CPU goes to power collapse frequently. For
>> example, playing audio while typically CPU remains idle.
>>
>> To enable deferrable timers,
>> $ echo 1> /sys/kernel/mm/ksm/deferrable_timer
>
> This could not have been the version which you tested. What's up?

My bad :( I will be careful next time
>
> --- a/mm/ksm.c~ksm-provide-support-to-use-deferrable-timers-for-scanner-thread-fix-fix-2
> +++ a/mm/ksm.c
> @@ -1720,8 +1720,6 @@ static int ksmd_should_run(void)
>
> static int ksm_scan_thread(void *nothing)
> {
> - signed long to;
> -
> set_freezable();
> set_user_nice(current, 5);
>
> @@ -1735,7 +1733,9 @@ static int ksm_scan_thread(void *nothing
> try_to_freeze();
>
> if (ksmd_should_run()) {
> - timeout = msecs_to_jiffies(ksm_thread_sleep_millisecs);
> + signed long to;
> +
> + to = msecs_to_jiffies(ksm_thread_sleep_millisecs);
> if (use_deferrable_timer)
> schedule_timeout_deferrable_interruptible(to);
> else
> _
>


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