linux-kernel - Re: [PATCH] SLUB: revert direct page allocator pass through

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Message-ID: <alpine.DEB.1.10.0902031159300.26129@qirst.com>
Date:	Tue, 3 Feb 2009 12:08:43 -0500 (EST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	yanmin_zhang@...ux.intel.com, Andi Kleen <andi@...stfloor.org>,
	Matthew Wilcox <matthew@....cx>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] SLUB: revert direct page allocator pass through

On Tue, 3 Feb 2009, Nick Piggin wrote:

> > A bitmap could be
> > used to avoid queuing and may even allow fully concurrent allocations
> > without locks. Use a counter to check watermarks once in a while.
>
> Bitmap? Involving locks or atomic operations, right?

Yes one could use a atomic operation there. The bitmap would be attached
to MAX_ORDER unit and if MAX_ORDER units would be assigned to a cpu for
allocation then the contention would be limited. The only contention would

> The page refcounting layer lives on top of the buddy/queueing/etc layers,
> so the same technique works no matter what the underlying allocator looks
> like.
>
> The only reason I didn't merge it is that it added another branch. I wanted
> to rework the APIs a little bit to avoid it.

Sounds good.

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