On Mon 16-07-12 21:52:51, Hugh Dickins wrote: > On Mon, 16 Jul 2012, Michal Hocko wrote: > > On Mon 16-07-12 01:35:34, Hugh Dickins wrote: > > > But even so, the test still OOMs sometimes: when originally testing > > > on 3.5-rc6, it OOMed about one time in five or ten; when testing > > > just now on 3.5-rc6-mm1, it OOMed on the first iteration. > > > > > > This residual problem comes from an accumulation of pages under > > > ordinary writeback, not marked PageReclaim, so rightly not causing > > > the memcg check to wait on their writeback: these too can prevent > > > shrink_page_list() from freeing any pages, so many times that memcg > > > reclaim fails and OOMs. > > > > I guess you managed to trigger this with 20M limit, right? > > That's right. > > > I have tested > > with different group sizes but the writeback didn't trigger for most of > > them and all the dirty data were flushed from the reclaim. > > I didn't examine writeback stats to confirm, but I guess that just > occasionally it managed to come in and do enough work to confound us. > > > Have you used any special setting the dirty ratio? > > No, I wasn't imaginative enough to try that. > > > Or was it with xfs (IIUC that one > > does ignore writeback from the direct reclaim completely). > > No, just ext4 at that point. > > I have since tested the final patch with ext4, ext3 (by ext3 driver > and by ext4 driver), ext2 (by ext2 driver and by ext4 driver), xfs, > btrfs, vfat, tmpfs (with swap on the USB stick) and block device: > about an hour on each, no surprises, all okay. > > But I didn't experiment beyond the 20M memcg. Great coverage anyway. Thanks a lot Hugh! > > Hugh -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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>