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

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Message-Id: <20090218093858.8990.A69D9226@jp.fujitsu.com>
Date:	Wed, 18 Feb 2009 09:48:09 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com,
	Pekka Enberg <penberg@...helsinki.fi>,
	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 Tue, 17 Feb 2009, Pekka Enberg wrote:
> 
> > >> +#define SLUB_MAX_SIZE (2 * PAGE_SIZE)
> >
> > On Tue, Feb 17, 2009 at 8:11 PM, Johannes Weiner <hannes@...xchg.org> wrote:
> > > This relies on PAGE_SIZE being 4k.  If you want 8k, why don't you say
> > > so?  Pekka did this explicitely.
> >
> > That could be a problem, sure. Especially for architecture that have 64 K pages.
> 
> You could likely put a complicated formula in there instead. But 2 *
> PAGE_SIZE is simple and will work on all platforms regardless of pagesize.

I think 2 * PAGE_SIZE is best and the patch description is needed change.
it's because almost architecture use two pages for stack and current page
allocator don't have delayed consolidation mechanism for order-1 page.

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!).

Am I misunderstand anything?



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