linux-kernel - init_timer_deferrable conversion

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Date:	Sun, 16 Dec 2007 22:00:23 -0500 (EST)
From:	Parag Warudkar <parag.warudkar@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: init_timer_deferrable conversion

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.

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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