linux-kernel - Re: [PATCH] scsi: fix sense

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Message-ID: <47FA94AE.4070803@cs.helsinki.fi>
Date:	Tue, 08 Apr 2008 00:39:58 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Hugh Dickins <hugh@...itas.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Lameter <clameter@....com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Jens Axboe <jens.axboe@...cle.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: fix sense_slab/bio swapping livelock

Linus Torvalds wrote:
>> I suspect the right thing to do is not to mark them for "IO", but mark 
>> them for "short-lived", and allow short-lived allocations that don't 
>> have extended lifetimes to succeed even when a "real" allocation 
>> wouldn't.

Pekka Enberg wrote:
> Yeah, makes sense. We do have GFP_TEMPORARY so we could associate this 
> new semantics with that. But the real problem here is how to do the 
> "allocate harder" part which, btw, sounds very similar to what Peter's 
> kmalloc reserve patches try to do...

Actually, a trivial way to implement that is to have a few "emergency 
kmalloc" caches say for sizes 64, 128, 256, and 512 that have some 
pre-allocated pages into which these GFP_TEMPORARY allocations are 
allowed to dip into on OOM and OOM only.

		Pekka
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