On Wed, Oct 13, 2010 at 04:10:43PM +0900, KOSAKI Motohiro wrote: > When memory shortage, we are using drain_pages() for flushing per cpu > page cache. In this case, per cpu stat should be flushed too. because > now we are under memory shortage and we need to know exact free pages. > > Otherwise get_page_from_freelist() may fail even though pcp was flushed. > With my patch adjusting the threshold to a small value while kswapd is awake, it seems less necessary. It's also very hard to predict the performance of this. We are certainly going to take a hit to do the flush but we *might* gain slightly if an allocation succeeds because a watermark check passed when the counters were updated. It's a definite hit for a possible gain though which is not a great trade-off. Would need some performance testing. I still think my patch on adjusting thresholds is our best proposal so far on how to reduce Shaohua's performance problems while still being safer from livelocks due to memory exhaustion. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>