On Fri 03-02-17 19:57:39, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Mon 30-01-17 09:55:46, Michal Hocko wrote: > > > On Sun 29-01-17 00:27:27, Tetsuo Handa wrote: > > [...] > > > > Regarding [1], it helped avoiding the too_many_isolated() issue. I can't > > > > tell whether it has any negative effect, but I got on the first trial that > > > > all allocating threads are blocked on wait_for_completion() from flush_work() > > > > in drain_all_pages() introduced by "mm, page_alloc: drain per-cpu pages from > > > > workqueue context". There was no warn_alloc() stall warning message afterwords. > > > > > > That patch is buggy and there is a follow up [1] which is not sitting in the > > > mmotm (and thus linux-next) yet. I didn't get to review it properly and > > > I cannot say I would be too happy about using WQ from the page > > > allocator. I believe even the follow up needs to have WQ_RECLAIM WQ. > > > > > > [1] http://lkml.kernel.org/r/20170125083038.rzb5f43nptmk7aed@xxxxxxxxxxxxxxxxxxx > > > > Did you get chance to test with this follow up patch? It would be > > interesting to see whether OOM situation can still starve the waiter. > > The current linux-next should contain this patch. > > So far I can't reproduce problems except two listed below (cond_resched() trap > in printk() and IDLE priority trap are excluded from the list). But I agree that > the follow up patch needs to use a WQ_RECLAIM WQ. It is theoretically possible > that an allocation request which can trigger the OOM killer waits for the > system_wq while there is already a work which is in system_wq which is looping > forever inside the page allocator without triggering the OOM killer. Well, this shouldn't happen AFAICS because a new worker would be requested and that would certainly require a memory and that allocation would trigger the OOM killer. On the other hand I agree that it would be safer to not depend on memory allocation from within the page allocator. > Maybe the follow up patch can share the vmstat WQ? Yes, this would be an option. -- 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>
