On Friday, January 20, 2017 6:39 PM Vlastimil Babka wrote: > > Changes since v1: > - add/remove comments per Michal Hocko and Hillf Danton > - move no_zone: label in patch 3 so we don't miss part of ac initialization > > This is v2 of my attempt to fix the recent report based on LTP cpuset stress > test [1]. The intention is to go to stable 4.9 LTSS with this, as triggering > repeated OOMs is not nice. That's why the patches try to be not too intrusive. > > Unfortunately why investigating I found that modifying the testcase to use > per-VMA policies instead of per-task policies will bring the OOM's back, but > that seems to be much older and harder to fix problem. I have posted a RFC [2] > but I believe that fixing the recent regressions has a higher priority. > > Longer-term we might try to think how to fix the cpuset mess in a better and > less error prone way. I was for example very surprised to learn, that cpuset > updates change not only task->mems_allowed, but also nodemask of mempolicies. > Until now I expected the parameter to alloc_pages_nodemask() to be stable. > I wonder why do we then treat cpusets specially in get_page_from_freelist() > and distinguish HARDWALL etc, when there's unconditional intersection between > mempolicy and cpuset. I would expect the nodemask adjustment for saving > overhead in g_p_f(), but that clearly doesn't happen in the current form. > So we have both crazy complexity and overhead, AFAICS. > > [1] > https://lkml.kernel.org/r/CAFpQJXUq-JuEP=QPidy4p_=fn0rkh5z-kfb4qbvsf6jms87...@mail.gmail.com > [2] https://lkml.kernel.org/r/7c459f26-13a6-a817-e508-b65b903a8...@suse.cz > > Vlastimil Babka (4): > mm, page_alloc: fix check for NULL preferred_zone > mm, page_alloc: fix fast-path race with cpuset update or removal > mm, page_alloc: move cpuset seqcount checking to slowpath > mm, page_alloc: fix premature OOM when racing with cpuset mems update > > include/linux/mmzone.h | 6 ++++- > mm/page_alloc.c | 68 > ++++++++++++++++++++++++++++++++++---------------- > 2 files changed, 52 insertions(+), 22 deletions(-) > Acked-by: Hillf Danton <hillf...@alibaba-inc.com>
