linux-kernel - Re: [PATCH -tip] mm: introduce __GFP

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Message-ID: <20090504193526.GC31176@lenovo>
Date:	Mon, 4 May 2009 23:35:26 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Ingo Molnar <mingo@...e.hu>, Rik van Riel <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [PATCH -tip] mm: introduce __GFP_PANIC modifier

[Mel Gorman - Mon, May 04, 2009 at 08:23:43PM +0100]
| On Mon, May 04, 2009 at 04:27:40PM +0400, Cyrill Gorcunov wrote:
| > Hi,
| > 
| > here is an attempt to bring in __GFP_PANIC modifier.
| > The patch is made on top of -tip repo. I've been
| > trying to apply it in top of -mm tree but it
| > seems -tip is a bit newer, at least it already
| > has __GFP_BITS_SHIFT = 22 defined.
| > 
| > Mel, could you take a look?
| > 
| 
| I'm not seeing any users of the new flag so I'm not sure what your intended
| use for the flag is.  Maybe it would have a small saving on call-sites that
| panic but as they are boot-time functions, I would expect the memory is
| getting freed anyway.

Yes they are boot-time, UV apic init at moment (already fixed via BUG_ON).
But I already noticed by Christoph that it's not a good idea to bring
this flag in. Sorry for bothering.

| 
| If this is about should_failslab(), can it be determined that we should not
| fail another way? For example, never randomly fail the allocation if the
| system is booting and __GFP_NOFAIL is specified.
| 
| > For easier review -- here is what is done:
| > 1) __GFP_PANIC introduced
| > 2) __alloc_pages_internal now checks for this flag
| >    and panic if needed.
| > 
| > 	-- Cyrill
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