linux-kernel - Re: [patch] SLQB slab allocator

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Message-Id: <1233624844.2604.106.camel@ymzhang>
Date:	Tue, 03 Feb 2009 09:34:04 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Hugh Dickins <hugh@...itas.com>, 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>
Subject: Re: [patch] SLQB slab allocator

On Mon, 2009-02-02 at 10:00 -0500, Christoph Lameter wrote:
> On Mon, 2 Feb 2009, Pekka Enberg wrote:
> 
> > Hi Yanmin,
> >
> > On Mon, 2009-02-02 at 11:38 +0800, Zhang, Yanmin wrote:
> > > Can we add a checking about free memory page number/percentage in function
> > > allocate_slab that we can bypass the first try of alloc_pages when memory
> > > is hungry?
> >
> > If the check isn't too expensive, I don't any reason not to. How would
> > you go about checking how much free pages there are, though? Is there
> > something in the page allocator that we can use for this?
> 
> If the free memory is low then reclaim needs to be run to increase the
> free memory.
I think reclaim did start often with Hugh's case. There would be no swap if not.

>  Falling back immediately incurs the overhead of going through
> the order 0 queues.
The falling back is temporal. Later on when there is enough free pages available,
new slab allocations go back to higher order automatically. This is to save the first
high-order allocation try because it often fails if memory is hungry.


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