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Subject: Re: [patch] SLQB slab allocator
From: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
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Date: Tue, 03 Feb 2009 09:34:04 +0800
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To: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>, Hugh Dickins <hugh@veritas.com>, Nick Piggin <npiggin@suse.de>, Linux Memory Management List <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Lin Ming <ming.m.lin@intel.com>
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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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