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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
