linux-kernel - Re: [GIT PULL v2] Early SLAB fixes for 2.6.31

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Date:	Wed, 17 Jun 2009 09:45:10 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Nick Piggin <npiggin@...e.de>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	kamezawa.hiroyu@...fujitsu.com, lizf@...fujitsu.com, mingo@...e.hu,
	yinghai@...nel.org
Subject: Re: [GIT PULL v2] Early SLAB fixes for 2.6.31

On Wed, 17 Jun 2009, Pekka Enberg wrote:
> 
> So how does the page allocator fit in this new scheme of things? I have
> been looking at doing the cleanups you and Christoph suggested and it
> seems to me we need a 'system_gfp_mask' that's respected by basically
> everyone, including __might_sleep() and other debugging functions.

So I'm very much ok with the whole "use magic gfp_mask to indicate what 
works at what stage". And yes, I think it makes sense to extend it to the 
page allocator and might_sleep too, because GFP_KERNEL has all the same 
issues regardless of whether it's about page allocation or about slab 
allocators. And any "might_sleep" suppression really does tend to be about 
the exact same thing.

So the only thing I was arguing against wrt Christoph was really that I 
think this thing should be an "internal" thing, and never ever be used as 
a flag for others to decide what to do. We do _not_ want drivers or other 
crazy people using it to decide what state they are running in. 

Keep it simple, and keep it minimal, in other words.

		Linus
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