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Date: Thu, 23 Apr 2009 01:19:08 +0100 From: Mel Gorman <mel@....ul.ie> To: David Rientjes <rientjes@...gle.com> Cc: Linux Memory Management List <linux-mm@...ck.org>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, Christoph Lameter <cl@...ux-foundation.org>, Nick Piggin <npiggin@...e.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Lin Ming <ming.m.lin@...el.com>, Zhang Yanmin <yanmin_zhang@...ux.intel.com>, Peter Zijlstra <peterz@...radead.org>, Pekka Enberg <penberg@...helsinki.fi>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH 16/22] Do not setup zonelist cache when there is only one node On Wed, Apr 22, 2009 at 01:24:26PM -0700, David Rientjes wrote: > On Wed, 22 Apr 2009, Mel Gorman wrote: > > > There is a zonelist cache which is used to track zones that are not in > > the allowed cpuset or found to be recently full. This is to reduce cache > > footprint on large machines. On smaller machines, it just incurs cost > > for no gain. This patch only uses the zonelist cache when there are NUMA > > nodes. > > > > Signed-off-by: Mel Gorman <mel@....ul.ie> > > Reviewed-by: Christoph Lameter <cl@...ux-foundation.org> > > --- > > mm/page_alloc.c | 7 +++++-- > > 1 files changed, 5 insertions(+), 2 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 7f45de1..e59bb80 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1467,8 +1467,11 @@ this_zone_full: > > if (NUMA_BUILD) > > zlc_mark_zone_full(zonelist, z); > > If zonelist caching is never used for UMA machines, why should they ever > call zlc_mark_zone_full()? It will always dereference > zonelist->zlcache_ptr and immediately return without doing anything. > > Wouldn't it better to just add > > if (num_online_nodes() == 1) > continue; > num_online_nodes() is actually a really heavy function. It calls hweight on a bitmap which is probably why it's not happening already. There is a nr_online_nodes later in the patchset though. With nr_online_nodes, it's a good idea to avoid a function call so I've taken note to do that patch in pass 2. Thanks > right before this call to zlc_mark_zone_full()? This should compile out > the remainder of the loop for !CONFIG_NUMA kernels anyway. > > > try_next_zone: > > - if (NUMA_BUILD && !did_zlc_setup) { > > - /* we do zlc_setup after the first zone is tried */ > > + if (NUMA_BUILD && !did_zlc_setup && num_online_nodes() > 1) { > > + /* > > + * we do zlc_setup after the first zone is tried but only > > + * if there are multiple nodes make it worthwhile > > + */ > > allowednodes = zlc_setup(zonelist, alloc_flags); > > zlc_active = 1; > > did_zlc_setup = 1; > > -- > > 1.5.6.5 > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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