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

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Message-ID: <alpine.LFD.2.01.0906170853580.16802@localhost.localdomain>
Date:	Wed, 17 Jun 2009 09:01:16 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Nick Piggin <npiggin@...e.de>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	cl@...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, Nick Piggin wrote:
> 
> In some cases perhaps it is difficult. In others it should be
> pretty natural. Lots of memory allocating paths pass gfp
> a long way down the stack.

I agree that some cases would be pretty natural. In fact, that's what we 
started out doing. On the x86 side, we didn't have a lot of issues in 
testing, and we fixed them up by using GFP_NOWAIT (see for example 
cpupri_init() in kernel/sched_cpupri.c, or init_irq_default_affinity() in 
kernel/irq/handle.c - both of which were fixed up in that phase).

Those paths, in fact, in general already had "bootmem" flags etc. And x86 
doesn't need to initialize a lot of state at bootup. 

Then Ben happened, and crazy PPC ioremap crap. 

So the problem is exactly that it was perfectly natural to pass down a gfp 
or other flag in _some_ cases. And then in a few cases it's much more 
painful.

		Linus
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