linux-ext4 - Re: [patch 1/5] mm: add nofail variants of kmalloc kcalloc and kzalloc

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Message-ID: <1282771677.1975.138.camel@laptop>
Date:	Wed, 25 Aug 2010 23:27:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Theodore Tso <tytso@....edu>, Jens Axboe <jaxboe@...ionio.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Brown <neilb@...e.de>, Alasdair G Kergon <agk@...hat.com>,
	Chris Mason <chris.mason@...cle.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Jan Kara <jack@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
	"linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
	"cluster-devel@...hat.com" <cluster-devel@...hat.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"reiserfs-devel@...r.kernel.org" <reiserfs-devel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [patch 1/5] mm: add nofail variants of kmalloc kcalloc and
 kzalloc

On Wed, 2010-08-25 at 14:11 -0700, David Rientjes wrote:
> 
> There's still no hard guarantee that the memory will allocatable 
> (GFP_KERNEL, the compaction, then GFP_ATOMIC could all still fail), but I 
> don't see how continuously looping the page allocator is possibly supposed 
> to help in these situations. 

Why do you think I'm a proponent of that behaviour?

I've been arguing that the existance of GFP_NOFAIL is the bug, and I
started the whole discussion because your patchset didn't outline the
purpose of its existance, it merely changes __GFP_NOFAIL usage into
$foo_nofail() functions, which on its own is a rather daft change.

Optimizing the page allocator by removing those conditional from its
innards into an outer loop not used by most callers seems a fine goal,
but you didn't state that.

Also, I like the postfix proposed by Andi better: _i_suck() :-)
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