On Wed, 2010-12-01 at 01:15 +0800, Mel Gorman wrote: > When the allocator enters its slow path, kswapd is woken up to balance the > node. It continues working until all zones within the node are balanced. For > order-0 allocations, this makes perfect sense but for higher orders it can > have unintended side-effects. If the zone sizes are imbalanced, kswapd > may reclaim heavily on a smaller zone discarding an excessive number of > pages. The user-visible behaviour is that kswapd is awake and reclaiming > even though plenty of pages are free from a suitable zone. > > This patch alters the "balance" logic to stop kswapd if any suitable zone > becomes balanced to reduce the number of pages it reclaims from other zones. from my understanding, the patch will break reclaim high zone if a low zone meets the high order allocation, even the high zone doesn't meet the high order allocation. This, for example, will make a high order allocation from a high zone fallback to low zone and quickly exhaust low zone, for example DMA. This will break some drivers. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>