On Fri 23-10-15 06:42:43, Tetsuo Handa wrote: > Tejun Heo wrote: > > On Thu, Oct 22, 2015 at 05:49:22PM +0200, Michal Hocko wrote: > > > I am confused. What makes rescuer to not run? Nothing seems to be > > > hogging CPUs, we are just out of workers which are loopin in the > > > allocator but that is preemptible context. > > > > It's concurrency management. Workqueue thinks that the pool is making > > positive forward progress and doesn't schedule anything else for > > execution while that work item is burning cpu cycles. > > Then, isn't below change easier to backport which will also alleviate > needlessly burning CPU cycles? This is quite obscure. If the vmstat_update fix needs workqueue tweaks as well then I would vote for your original patch which is clear, straightforward and easy to backport. If WQ_MEM_RECLAIM can really guarantee one worker as described in the documentation then I agree that fixing vmstat is a better fix. But that doesn't seem to be the case currently. > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3385,6 +3385,7 @@ retry: > ((gfp_mask & __GFP_REPEAT) && pages_reclaimed < (1 << order))) { > /* Wait for some write requests to complete then retry */ > wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC, HZ/50); > + schedule_timeout_uninterruptible(1); > goto retry; > } > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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>