On Thu, Dec 15, 2011 at 11:38:43PM -0500, Rik van Riel wrote: > On 12/14/2011 10:41 AM, Mel Gorman wrote: > >If compaction can proceed for a given zone, shrink_zones() does not > >reclaim any more pages from it. After commit [e0c2327: vmscan: abort > >reclaim/compaction if compaction can proceed], do_try_to_free_pages() > >tries to finish as soon as possible once one zone can compact. > > > >This was intended to prevent slabs being shrunk unnecessarily but > >there are side-effects. One is that a small zone that is ready for > >compaction will abort reclaim even if the chances of successfully > >allocating a THP from that zone is small. It also means that reclaim > >can return too early even though sc->nr_to_reclaim pages were not > >reclaimed. > > Having slabs shrunk "too much" might actually be good, > because it does result in more memory blocks where > compaction can be successful. > > If we end up frequently evicting frequently accessed > data from the slab cache, chances are the buffer cache > will cache that data (since we reload it often). > > If we end up evicting infrequently used data, chances > are it won't really matter for performance. > True, but I was being mindful of Dave Chinners recent work on preventing slab cache being dumped entirely. There still may be an impact to metadata-intensive workloads although I did not spot any problems myself. > >This partially reverts the commit until it is proven that slabs are > >really being shrunk unnecessarily but preserves the check to return > >1 to avoid OOM if reclaim was aborted prematurely. > > > >[aarcange@xxxxxxxxxx: This patch replaces a revert from Andrea] > >Signed-off-by: Mel Gorman<mgorman@xxxxxxx> > > Reviewed-by: Rik van Riel<riel@xxxxxxxxxx> > Thanks. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>