On Mon, 9 Jun 2014, Vlastimil Babka wrote: > Unlike the migration scanner, the free scanner remembers the beginning of the > last scanned pageblock in cc->free_pfn. It might be therefore rescanning pages > uselessly when called several times during single compaction. This might have > been useful when pages were returned to the buddy allocator after a failed > migration, but this is no longer the case. > > This patch changes the meaning of cc->free_pfn so that if it points to a > middle of a pageblock, that pageblock is scanned only from cc->free_pfn to the > end. isolate_freepages_block() will record the pfn of the last page it looked > at, which is then used to update cc->free_pfn. > > In the mmtests stress-highalloc benchmark, this has resulted in lowering the > ratio between pages scanned by both scanners, from 2.5 free pages per migrate > page, to 2.25 free pages per migrate page, without affecting success rates. > > Signed-off-by: Vlastimil Babka <vba...@suse.cz> > Cc: Minchan Kim <minc...@kernel.org> > Cc: Mel Gorman <mgor...@suse.de> > Cc: Joonsoo Kim <iamjoonsoo....@lge.com> > Cc: Michal Nazarewicz <min...@mina86.com> > Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com> > Cc: Christoph Lameter <c...@linux.com> > Cc: Rik van Riel <r...@redhat.com> > Cc: David Rientjes <rient...@google.com>
Acked-by: David Rientjes <rient...@google.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
