RE: [PATCH] bdi: use deferable timer for sync_supers task

[Wu, Xia]

On Fri, Oct 08, 2010 at 04:35:14PM +0800, Yong Wang wrote:
> > sync_supers task currently wakes up periodically for superblock
> > writeback. This hurts power on battery driven devices. This patch
> > turns this housekeeping timer into a deferable timer so that it
> > does not fire when system is really idle.

> How long can the timer be defereed?  We can't simply stop writing
> out data for a long time.  I think the current timer value should be
> the upper bound, but allowing to fire earlier to run during the
> same wakeup cycle as others is fine.

If the system is in sleep state, this timer can be deferred to the next wake-up interrupt.
If the system is busy, this timer will fire at the scheduled time.


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