Messages in this thread Patch in this message | | | Date | Mon, 18 May 2009 11:49:07 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH 4/4] zone_reclaim_mode is always 0 by default |
| |
On Wed, May 13, 2009 at 12:08:12PM +0900, KOSAKI Motohiro wrote: > Subject: [PATCH] zone_reclaim_mode is always 0 by default > > Current linux policy is, if the machine has large remote node distance, > zone_reclaim_mode is enabled by default because we've be able to assume to > large distance mean large server until recently. > > Unfrotunately, recent modern x86 CPU (e.g. Core i7, Opeteron) have P2P transport > memory controller. IOW it's NUMA from software view. > > Some Core i7 machine has large remote node distance and zone_reclaim don't > fit desktop and small file server. it cause performance degression.
I can confirm this, Yanmin recently ran into exactly such a regression, which was fixed by manually disabling the zone reclaim mode. So I guess you can safely add an
Tested-by: "Zhang, Yanmin" <yanmin.zhang@intel.com>
> Thus, zone_reclaim == 0 is better by default. sorry, HPC gusy. > you need to turn zone_reclaim_mode on manually now.
I guess the borderline will continue to blur up. It will be more dependent on workloads instead of physical NUMA capabilities. So
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Cc: Christoph Lameter <cl@linux-foundation.org> > Cc: Rik van Riel <riel@redhat.com> > --- > mm/page_alloc.c | 7 ------- > 1 file changed, 7 deletions(-) > > Index: b/mm/page_alloc.c > =================================================================== > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2494,13 +2494,6 @@ static void build_zonelists(pg_data_t *p > int distance = node_distance(local_node, node); > > /* > - * If another node is sufficiently far away then it is better > - * to reclaim pages in a zone before going off node. > - */ > - if (distance > RECLAIM_DISTANCE) > - zone_reclaim_mode = 1; > - > - /* > * We don't want to pressure a particular node. > * So adding penalty to the first node in same > * distance group to make it round-robin. > > > -- > 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
| |