On Wed, Jul 16, 2014 at 03:48:18PM +0200, 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. > > With __GFP_NO_KSWAPD allocations, this appears to result in a worse ratio (2.1 > instead of 1.8), but page migration successes increased by 10%, so this could > mean that more useful work can be done until need_resched() aborts this kind > of compaction. > > Signed-off-by: Vlastimil Babka <[email protected]> > Reviewed-by: Zhang Yanfei <[email protected]> > Reviewed-by: Naoya Horiguchi <[email protected]> > Acked-by: David Rientjes <[email protected]> > Acked-by: Minchan Kim <[email protected]>
Acked-by: Mel Gorman <[email protected]> -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
