linux-kernel - Re: [PATCH v2] slab,slub: ignore __GFP_WAIT if we're booting or suspending

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Message-ID: <20090621061847.GB1474@ucw.cz>
Date:	Sun, 21 Jun 2009 08:18:47 +0200
From:	Pavel Machek <pavel@....cz>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Pekka J Enberg <penberg@...helsinki.fi>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu, npiggin@...e.de,
	akpm@...ux-foundation.org, cl@...ux-foundation.org,
	torvalds@...ux-foundation.org, "Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH v2] slab,slub: ignore __GFP_WAIT if we're booting or
	suspending

Hi!

> > Academic for boot, probably real for suspend/resume. There the atomic
> > reserves could matter because the memory can be pretty full when you
> > start suspend.
> 
> Right, that might be something to look into, though we haven't yet
> applied the technique for suspend & resume. My main issue with it at the
> moment is how do I synchronize with allocations that are already
> sleeping when changing the gfp flag mask without bloating the normal

Well, but the problem already exists, no? If someone is already
sleeping due to __GFP_WAIT, he'll probably sleep till the resume.

...well, if he's sleeping in the disk driver, I suspect driver will
finish outstanding requests as part of .suspend().

> I also suspect that we might want to try to make -some- amount of free
> space before starting suspend, though of course not nearly as
> aggressively as with std.

We free 4MB in 2.6.30, but Rafael is removing that for 2.6.31 :-(.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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