From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 3 Jul 2008 17:38:37 +0100 From: Mel Gorman Subject: Re: [problem] raid performance loss with 2.6.26-rc8 on 32-bit x86 (bisected) Message-ID: <20080703163836.GD18055@csn.ul.ie> References: <20080701080910.GA10865@csn.ul.ie> <20080701175855.GI32727@shadowen.org> <20080701190741.GB16501@csn.ul.ie> <1214944175.26855.18.camel@dwillia2-linux.ch.intel.com> <20080702051759.GA26338@csn.ul.ie> <1215049766.2840.43.camel@dwillia2-linux.ch.intel.com> <20080703042750.GB14614@csn.ul.ie> <20080703050036.GD14614@csn.ul.ie> <1215064455.15797.4.camel@dwillia2-linux.ch.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1215064455.15797.4.camel@dwillia2-linux.ch.intel.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Dan Williams Cc: Linus Torvalds , Andy Whitcroft , linux-mm@kvack.org, linux-kernel@vger.kernel.org, NeilBrown , babydr@baby-dragons.com, cl@linux-foundation.org, lee.schermerhorn@hp.com, a.beregalov@gmail.com, akpm@linux-foundation.org List-ID: On (02/07/08 22:54), Dan Williams didst pronounce: > > On Wed, 2008-07-02 at 22:00 -0700, Mel Gorman wrote: > > > Subject: [PATCH] Do not overwrite nr_zones on !NUMA when initialising zlcache_ptr > > > > With the two-zonelist patches on !NUMA machines, there really is only one > > zonelist as __GFP_THISNODE is meaningless. However, during initialisation, the > > assumption is made that two zonelists exist when initialising zlcache_ptr. The > > result is that pgdat->nr_zones is always 0. As kswapd uses this value to > > determine what reclaim work is necessary, the result is that kswapd never > > reclaims. This causes processes to stall frequently in low-memory situations > > as they always direct reclaim. This patch initialises zlcache_ptr correctly. > > > > Signed-off-by: Mel Gorman > > --- > > page_alloc.c | 1 - > > 1 file changed, 1 deletion(-) > > > > diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.26-rc8-clean/mm/page_alloc.c linux-2.6.26-rc8-fix-kswapd-on-numa/mm/page_alloc.c > > --- linux-2.6.26-rc8-clean/mm/page_alloc.c 2008-06-24 18:58:20.000000000 -0700 > > +++ linux-2.6.26-rc8-fix-kswapd-on-numa/mm/page_alloc.c 2008-07-02 21:49:09.000000000 -0700 > > @@ -2328,7 +2328,6 @@ static void build_zonelists(pg_data_t *p > > static void build_zonelist_cache(pg_data_t *pgdat) > > { > > pgdat->node_zonelists[0].zlcache_ptr = NULL; > > - pgdat->node_zonelists[1].zlcache_ptr = NULL; > > } > > > > #endif /* CONFIG_NUMA */ > > > > Bug squished. > > # for i in `seq 1 5`; do dd if=/dev/zero of=/dev/md0 bs=1024k count=2048; done > 2048+0 records in > 2048+0 records out > 2147483648 bytes (2.1 GB) copied, 7.73352 s, 278 MB/s > 2048+0 records in > 2048+0 records out > 2147483648 bytes (2.1 GB) copied, 7.6845 s, 279 MB/s > 2048+0 records in > 2048+0 records out > 2147483648 bytes (2.1 GB) copied, 7.74428 s, 277 MB/s > 2048+0 records in > 2048+0 records out > 2147483648 bytes (2.1 GB) copied, 7.65959 s, 280 MB/s > 2048+0 records in > 2048+0 records out > 2147483648 bytes (2.1 GB) copied, 7.73107 s, 278 MB/s > > Tested-by: Dan Williams > Great news. Dan, thanks a lot for reporting and persisting with the testing of various bits and pieces to get this pinned down. It is greatly appreciated. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org