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Message-ID: <Pine.LNX.4.64.0710011354480.19779@schroedinger.engr.sgi.com>
Date: Mon, 1 Oct 2007 13:55:29 -0700 (PDT)
From: Christoph Lameter <clameter@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Nick Piggin <nickpiggin@...oo.com.au>,
Christoph Hellwig <hch@....de>, Mel Gorman <mel@...net.ie>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
David Chinner <dgc@....com>, Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK
On Sat, 29 Sep 2007, Andrew Morton wrote:
> > atomic allocations. And with SLUB using higher order pages, atomic !0
> > order allocations will be very very common.
>
> Oh OK.
>
> I thought we'd already fixed slub so that it didn't do that. Maybe that
> fix is in -mm but I don't think so.
>
> Trying to do atomic order-1 allocations on behalf of arbitray slab caches
> just won't fly - this is a significant degradation in kernel reliability,
> as you've very easily demonstrated.
Ummm... SLAB also does order 1 allocations. We have always done them.
See mm/slab.c
/*
* Do not go above this order unless 0 objects fit into the slab.
*/
#define BREAK_GFP_ORDER_HI 1
#define BREAK_GFP_ORDER_LO 0
static int slab_break_gfp_order = BREAK_GFP_ORDER_LO;
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