On Fri 01-12-17 14:33:17, Johannes Weiner wrote: > On Sat, Nov 25, 2017 at 07:52:47PM +0900, Tetsuo Handa wrote: > > @@ -1068,6 +1071,17 @@ bool out_of_memory(struct oom_control *oc) > > } > > > > select_bad_process(oc); > > + /* > > + * Try really last second allocation attempt after we selected an OOM > > + * victim, for somebody might have managed to free memory while we were > > + * selecting an OOM victim which can take quite some time. > > Somebody might free some memory right after this attempt fails. OOM > can always be a temporary state that resolves on its own. > > What keeps us from declaring OOM prematurely is the fact that we > already scanned the entire LRU list without success, not last second > or last-last second, or REALLY last-last-last-second allocations. You are right that this is inherently racy. The point here is, however, that the race window between the last check and the kill can be _huge_! Another argument is that the allocator itself could have changed its allocation capabilities - e.g. become the OOM victim itself since the last time it the allocator could have reflected that fact. So this is a pragmatic way to reduce weird corner cases while the overal complexity doesn't grow too much. > Nacked-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- 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>
