Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756751AbXKCRid (ORCPT ); Sat, 3 Nov 2007 13:38:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754893AbXKCRi1 (ORCPT ); Sat, 3 Nov 2007 13:38:27 -0400 Received: from 1wt.eu ([62.212.114.60]:3658 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754882AbXKCRi0 (ORCPT ); Sat, 3 Nov 2007 13:38:26 -0400 Date: Sat, 3 Nov 2007 18:38:07 +0100 From: Willy Tarreau To: Hugh Dickins Cc: Christoph Lameter , Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-stable@vger.kernel.org Subject: Re: [PATCH 1/2] slub: fix leakage Message-ID: <20071103173807.GB1045@1wt.eu> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1968 Lines: 49 On Sat, Nov 03, 2007 at 05:10:54PM +0000, Hugh Dickins wrote: > Slub has been quite leaky under load. Taking mm_struct as an example, in > a loop of swapping kernel builds, after the first iteration slabinfo shows: > Name Objects Objsize Space Slabs/Part/Cpu O/S O %Fr %Ef Flg > mm_struct 55 840 73.7K 18/7/4 4 0 38 62 A > but Objects and Partials steadily creep up - after the 340th iteration: > mm_struct 110 840 188.4K 46/36/4 4 0 78 49 A > > The culprit turns out to be __slab_alloc(), where it copes with the race > that another task has assigned the cpu slab while we were allocating one. > Don't rush off to load_freelist there: that assumes c->freelist is empty, > and will lose all of its free slots when c->page->freelist is not empty. > Instead just do a local allocation from c->freelist when it has one. > > Which fixes the leakage: Objects and Partials then remain stable. > > Signed-off-by: Hugh Dickins > --- > I recommend this for 2.6.24-rc2 and 2.6.23-stable. Hugh, you should also have CC'd linux-stable for this, otherwise there's a risk that the patch remains unnoticed by the stable team (CC'd). > mm/slub.c | 5 +++++ > 1 file changed, 5 insertions(+) > > --- 2.6.24-rc1/mm/slub.c 2007-10-24 07:16:04.000000000 +0100 > +++ linux/mm/slub.c 2007-11-03 13:22:31.000000000 +0000 > @@ -1525,6 +1525,11 @@ new_slab: > * want the current one since its cache hot > */ > discard_slab(s, new); > + if (c->freelist) { > + object = c->freelist; > + c->freelist = object[c->offset]; > + return object; > + } > slab_lock(c->page); > goto load_freelist; > } Regards, Willy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/