On 11/25/2015 01:00 PM, Michal Hocko wrote: > On Tue 24-11-15 15:22:03, Joonsoo Kim wrote: >> When I tested compaction in low memory condition, I found that >> my benchmark is stuck in congestion_wait() at shrink_inactive_list(). >> This stuck last for 1 sec and after then it can escape. More investigation >> shows that it is due to stale vmstat value. vmstat is updated every 1 sec >> so it is stuck for 1 sec. > > Wouldn't it be sufficient to use zone_page_state_snapshot in > too_many_isolated? That sounds better than the ad-hoc half-solution, yeah. I don't know how performance sensitive the callers are, but maybe it could do a non-snapshot check first, and only repeat with _snapshot when it's about to wait (the result is true), just to make sure? OTOH, how big issue is this? I suspect the system has been genuinely too_many_isolated(), or very close, in order to hit the condition in the first place, and the inaccuracy just delays the recovery a bit? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>