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

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Message-Id: <1245923793.22312.5.camel@pasglop>
Date:	Thu, 25 Jun 2009 19:56:33 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Pavel Machek <pavel@....cz>,
	Pekka J Enberg <penberg@...helsinki.fi>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	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

> Maybe so. Masking off __GFP_WAIT up in slab and page allocator
> isn't really needed though (or necessarily a good idea to throw
> out that information far from where it is used).
> 
> Checking for suspend active and avoiding writeout from reclaim
> for example might be a better idea.

Ah ok. Yes, I agree. I'm not familiar with those code path and
so masking gfp here sounded like the easier solution but you may well be
right here :-)
 
> > So yes, just applying the mask would help, but wouldn't completely fix
> > it unless we also find a way to synchronize.
> 
> You could potentially use srcu or something like that in page
> reclaim in order to have a way to be able to kick everyone
> out. page reclaim entry/exit from the page allocator isn't such
> a fastpath though, so even a simple mutex or something may be
> possible.

Ok. Well, I'll leave that to the suspend/resume folks for now, as I'm
way too busy at the moment to give that a serious look, but thanks for
the pointer.

Cheers,
Ben.

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