On Wed, Aug 18, 2010 at 09:51:23AM +0100, Mel Gorman wrote: > > What's a window low and min wmark? Maybe I can miss your point. > > > > The window is due to the fact kswapd is not awake yet. The window is because > kswapd might not be awake as NR_FREE_PAGES is higher than it should be. The > system is really somewhere between the low and min watermark but we are not > taking the accurate measure until kswapd gets woken up. The first allocation > to notice we are below the low watermark (be it due to vmstat refreshing or > that NR_FREE_PAGES happens to report we are below the watermark regardless of > any drift) wakes kswapd and other callers then take an accurate count hence > "we could breach the watermark but I'm expecting it can only happen for at > worst one allocation". Right. I misunderstood your word. One more question. Could you explain live lock scenario? I looked over the code. Although the VM pass zone_watermark_ok by luck, It can't allocate the page from buddy and then might go OOM. When do we meet live lock case? I think the description in change log would be better to understand this patch in future. Thanks. -- Kind regards, Minchan Kim -- 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>