Messages in this thread | | | Date | Tue, 9 Jun 2009 09:50:38 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 3/3] Do not unconditionally treat zones that fail zone_reclaim() as full |
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On Tue, Jun 09, 2009 at 11:11:19AM +0800, Wu Fengguang wrote: > On Mon, Jun 08, 2009 at 09:01:30PM +0800, Mel Gorman wrote: > > On NUMA machines, the administrator can configure zone_reclaim_mode that > > is a more targetted form of direct reclaim. On machines with large NUMA > > distances for example, a zone_reclaim_mode defaults to 1 meaning that clean > > unmapped pages will be reclaimed if the zone watermarks are not being > > met. The problem is that zone_reclaim() failing at all means the zone > > gets marked full. > > > > This can cause situations where a zone is usable, but is being skipped > > because it has been considered full. Take a situation where a large tmpfs > > mount is occuping a large percentage of memory overall. The pages do not > > get cleaned or reclaimed by zone_reclaim(), but the zone gets marked full > > and the zonelist cache considers them not worth trying in the future. > > > > This patch makes zone_reclaim() return more fine-grained information about > > what occured when zone_reclaim() failued. The zone only gets marked full if > > it really is unreclaimable. If it's a case that the scan did not occur or > > if enough pages were not reclaimed with the limited reclaim_mode, then the > > zone is simply skipped. > > > > There is a side-effect to this patch. Currently, if zone_reclaim() > > successfully reclaimed SWAP_CLUSTER_MAX, an allocation attempt would > > go ahead. With this patch applied, zone watermarks are rechecked after > > zone_reclaim() does some work. > > > > Signed-off-by: Mel Gorman <mel@csn.ul.ie> > > Thanks for making the code a lot more readable :) > > Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> >
Thanks.
> > /* > > * Do not scan if the allocation should not be delayed. > > */ > > if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) > > - return 0; > > + return ZONE_RECLAIM_NOSCAN; > > Why not kill the extra tab? >
Why not indeed. Tab is now killed.
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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