On Wed, 16 Feb 2011 09:50:49 +0000 Mel Gorman <mel@xxxxxxxxx> wrote: > should_continue_reclaim() for reclaim/compaction allows scanning to continue > even if pages are not being reclaimed until the full list is scanned. In > terms of allocation success, this makes sense but potentially it introduces > unwanted latency for high-order allocations such as transparent hugepages > and network jumbo frames that would prefer to fail the allocation attempt > and fallback to order-0 pages. Worse, there is a potential that the full > LRU scan will clear all the young bits, distort page aging information and > potentially push pages into swap that would have otherwise remained resident. afaict the patch affects order-0 allocations as well. What are the implications of this? Also, what might be the downsides of this change, and did you test for them? > This patch will stop reclaim/compaction if no pages were reclaimed in the > last SWAP_CLUSTER_MAX pages that were considered. a) Why SWAP_CLUSTER_MAX? Is (SWAP_CLUSTER_MAX+7) better or worse? b) The sentence doesn't seem even vaguely accurate. shrink_zone() will scan vastly more than SWAP_CLUSTER_MAX pages before calling should_continue_reclaim(). Confused. c) The patch doesn't "stop reclaim/compaction" fully. It stops it against one zone. reclaim will then advance on to any other eligible zones. -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>