On Wed 25-11-15 14:43:38, Vlastimil Babka wrote: > 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? I am not sure this is worth bothering. We are in the reclaim which is not a hot path. -- Michal Hocko SUSE Labs -- 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>