On Tue, Jan 26, 2016 at 06:07:52PM +0100, Vlastimil Babka wrote: > On 01/25/2016 07:45 PM, Johannes Weiner wrote: > >>>- One of the long lasting issue related to the OOM handling is when to > >>> actually declare OOM. There are workloads which might be trashing on > >>> few last remaining pagecache pages or on the swap which makes the > >>> system completely unusable for considerable amount of time yet the > >>> OOM killer is not invoked. Can we finally do something about that? > >I'm working on this, but it's not an easy situation to detect. > > > >We can't decide based on amount of page cache, as you could have very > >little of it and still be fine. Most of it could still be used-once. > > > >We can't decide based on number or rate of (re)faults, because this > >spikes during startup and workingset changes, or can be even sustained > >when working with a data set that you'd never expect to fit into > >memory in the first place, while still making acceptable progress. > > I would hope that workingset should help distinguish workloads thrashing due > to low memory and those that can't fit there no matter what? Or would it > require tracking lifetime of so many evicted pages that the memory overhead > of that would be infeasible? Yes, using the workingset code is exactly my plan. The only thing it requires on top is a time component. Then we can kick the OOM killer based on the share of time a workload (the system?) spends thrashing. -- 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>