On Fri, Aug 02, 2013 at 11:37:24AM -0400, Johannes Weiner wrote: > When the page allocator fails to get a page from all zones in its > given zonelist, it wakes up the per-node kswapds for all zones that > are at their low watermark. > > However, with a system under load the free pages in a zone can > fluctuate enough that the allocation fails but the kswapd wakeup is > also skipped while the zone is still really close to the low > watermark. > > When one node misses a wakeup like this, it won't be aged before all > the other node's zones are down to their low watermarks again. And > skipping a full aging cycle is an obvious fairness problem. > > Kswapd runs until the high watermarks are restored, so it should also > be woken when the high watermarks are not met. This ages nodes more > equally and creates a safety margin for the page counter fluctuation. > > By using zone_balanced(), it will now check, in addition to the > watermark, if compaction requires more order-0 pages to create a > higher order page. > > Signed-off-by: Johannes Weiner <han...@cmpxchg.org> > Reviewed-by: Rik van Riel <r...@redhat.com>
Acked-by: Mel Gorman <mgor...@suse.de> -- Mel Gorman SUSE Labs -- 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/
