On Fri, 25 Jul 2014 20:18:18 +0530 Chintan Pandya <cpandya@xxxxxxxxxxxxxx> 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?
--- 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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