On Sun, 16 Dec 2007 22:00:23 -0500 (EST)
Parag Warudkar <[email protected]> wrote:
> In my quest to get the wake-ups from idle per second down to bare minimum,
> I noticed 3 places in the kernel that could benefit from
> using init_timer_deferrable() instead of init_timer() -
>
> a) drivers/net/sky2.c - watchdog_timer. This was showing up high on
> Powertop's list of things that cause routine wakeups from idle. After
> converting to init_timer_deferrable() the wakeups went down and this one
> no longer shows up in powertop's list. 25% reduction.
>
> b) kernel/time/clocksource.c - watchdog_timer - same story as sky2.c
>
> c) net/core/neighbour.c - gc_timer - Most benefit from deferrable timer.
neigh_periodic_timer() is actually doing almost nothing per round, since it
looks only one slot of hash table. We could probably convert it to a
workqueue and scan whole table at once.
>
> I am running a kernel with above changes and haven't noticed any immediate
> problems and the wakeups-from-idle have gone down from 5-7 to mere 1-2 per
> second.
>
> Is there any reason not to make the above timers deferrable - corner
> cases, other side effects? If not then I will submit a patch.
>
> Thanks
>
> Parag
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