On Wed, Sep 24, 2014 at 05:22:32PM +0200, Vlastimil Babka wrote: > On 08/26/2014 09:30 AM, Minchan Kim wrote: > >Recently, I saw several reports that high order allocation failed > >although there were many freeable pages but it's hard to reproduce > >so asking them to reproduce the problem several time is really painful. > > > >A culprit I doubt is compaction deferring logic which prevent > >compaction for a while so high order allocation could be fail. > > Could be that, but also the non-determinism of watermark checking, > where compaction thinks allocation should succeed, but in the end it > won't. > > >It would be more clear if we can see the stat which can show > >current zone's compaction deferred state when allocatil fail. > > > >It's a RFC and never test it. I just get an idea with > >handling another strange high order allocation fail. > >Any comments are welcome. > > It's quite large patch. Maybe it could be much simpler if you did > not print just true/false but: > > 1) true/false based on zone->compact_considered < defer_limit, ignoring > zone->compact_order_failed > > 2) zone->compact_order_failed value itself > > Then you wouldn't need to pass the allocation order around like you do. > The "allocation failed" message tells you the order which was > attempted, and then it's easy for the user to compare with the > reported > zone->compact_order_failed and decide if the defer status actually > applies or not. Actually, I thought about it. The reason I avoid that approach is I don't want to expose deferring logic internal but now that I think about it, it was wrong conclusion because show_free_area already have been exported lots of internal. IOW, without it, there is not much to investigate the reason. I will send it. Thanks for the review, Vlastimil. > > > -- > 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> -- Kind regards, Minchan Kim -- 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>