linux-kernel - Re: [patch] SLQB slab allocator (try 2)

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Date:	Thu, 19 Feb 2009 11:16:07 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mel@....ul.ie>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Nick Piggin <npiggin@...e.de>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lin Ming <ming.m.lin@...el.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Subject: Re: [patch] SLQB slab allocator (try 2)

On Wed, 2009-02-18 at 09:48 +0900, KOSAKI Motohiro wrote:
> > > In addition, if pekka patch (SLAB_LIMIT = 8K) run on ia64, 16K allocation 
> > > always fallback to page allocator and using 64K (4 times memory consumption!).
> > 
> > Yes, correct, but SLUB does that already by passing all allocations over
> > 4K to the page allocator.
> 
> hmhm
> OK. my mail was pointless.
> 
> but why? In my understanding, slab framework mainly exist for efficient
> sub-page allocation.
> the fallbacking of 4K allocation in 64K page-sized architecture seems
> inefficient.

I don't think any of the slab allocators are known for memory
efficiency. That said, the original patch description sums up the
rationale for page allocator pass-through:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=aadb4bc4a1f9108c1d0fbd121827c936c2ed4217

Interesting enough, there seems to be some performance gain from it as
well as seen by Mel Gorman's recent slab allocator benchmarks.

			Pekka

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