On Fri, 10 Dec 2010 15:46:20 +0000 Mel Gorman <mel@xxxxxxxxx> 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 within a smaller zone discarding an excessive number of > pages. Why was it doing this? > The user-visible behaviour is that kswapd is awake and reclaiming > even though plenty of pages are free from a suitable zone. Suitable for what? I assume you refer to a future allocation which can be satisfied from more than one of the zones? But what if that allocation wanted to allocate a high-order page from a zone which we just abandoned? > This patch alters the "balance" logic for high-order reclaim allowing kswapd > to stop if any suitable zone becomes balanced to reduce the number of pages again, suitable for what? > it reclaims from other zones. kswapd still tries to ensure that order-0 > watermarks for all zones are met before sleeping. Handling order-0 pages differently from higher-order pages sounds weird and wrong. I don't think I understand this patch. -- 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>