linux-kernel - Re: slab: setup allocators earlier in the boot sequence

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Date:	Fri, 12 Jun 2009 17:04:17 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, mingo@...e.hu,
	akpm@...ux-foundation.org, npiggin@...e.de
Subject: Re: slab: setup allocators earlier in the boot sequence

Hi Ben,

On Sat, 2009-06-13 at 00:02 +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2009-06-12 at 16:54 +0300, Pekka Enberg wrote:
> > Hi Christoph,
> > 
> > On Fri, 2009-06-12 at 09:49 -0400, Christoph Lameter wrote:
> > > Best thing to do is to recognize the fact that we are still in early boot
> > > in the allocators. Derived allocators (such as slab and vmalloc) mask bits
> > > using GFP_RECLAIM_MASK and when doing allocations through the page
> > > allocator. You could make GFP_RECLAIM_MASK a variable. During boot
> > > __GFP_WAIT would not be set in GFP_RECLAIM_MASK.
> > 
> > Ben's patch does something like that and I have patches that do that
> > floating around too.
> > 
> > The problem here is that it's not enough that we make GFP_RECLAIM_MASK a
> > variable. There are various _debugging checks_ that happen much earlier
> > than that. We need to mask out those too which adds overhead to
> > kmalloc() fastpath, for example.
> 
> Hrm... I though I stuck my masking before the lockdep tests but maybe I
> missed some...

Your patch is fine but what Christoph suggested is not (at least the way
I understood it).

			Pekka

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