Re: [PATCH 2/2] UBIFS: start using hrtimers

From: Artem Bityutskiy
Date: Fri May 29 2009 - 10:02:19 EST

Peter Zijlstra wrote:
On Fri, 2009-05-29 at 18:09 +0300, Artem Bityutskiy wrote:
From: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>
Subject: [PATCH 2/2] UBIFS: start using hrtimers

UBIFS uses timers for write-buffer write-back. It is not
crucial for us to write-back exactly on time. We are fine
to write-back a little earlier or later. And this means
we may optimize UBIFS timer so that it could be groped
with a close timer event, so that the CPU would not be
waken up just to do the write back. This is optimization
to lessen power consumption, which is important in
embedded devices UBIFS is used for.

hrtimers have a nice feature: they are effectively range
timers, and we may defind the soft and hard limits for
it. Standard timers do not have these feature. They may
only be made deferrable, but this means there is effectively
no hard limit. So, we will better use hrtimers.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@xxxxxxxxx>

Seems sane enough from a hrtimer POV, but isn't this already
functionality that the VFS/pdflush provide?

And I also have a longer term plan to switch the VFS/pdflush
timer to be a range hrtimer, BTW, just like you suggested
me once.

Best Regards,
Artem Bityutskiy (ÐÑÑÑÐ ÐÐÑÑÑÐÐÐ)
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