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SubjectRe: [RFC PATCH v2 0/3] oom: rework oom_reaper vs. exit_mmap handoff
On Thu 25-10-18 10:24:00, Michal Hocko wrote:
> The previous version of this RFC has been posted here [1]. I have fixed
> few issues spotted during the review and by 0day bot. I have also reworked
> patch 2 to be ratio rather than an absolute number based.
>
> With this series applied the locking protocol between the oom_reaper and
> the exit path is as follows.
>
> All parts which cannot race should use the exclusive lock on the exit
> path. Once the exit path has passed the moment when no blocking locks
> are taken then it clears mm->mmap under the exclusive lock. oom_reaper
> checks for this and sets MMF_OOM_SKIP only if the exit path is not guaranteed
> to finish the job. This is patch 3 so see the changelog for all the details.
>
> I would really appreciate if David could give this a try and see how
> this behaves in workloads where the oom_reaper falls flat now. I have
> been playing with sparsely allocated memory with a high pte/real memory
> ratio and large mlocked processes and it worked reasonably well.

Does this help workloads you were referring to earlier David?

> There is still some room for tuning here of course. We can change the
> number of retries for the oom_reaper as well as the threshold when the
> keep retrying.
>
> Michal Hocko (3):
> mm, oom: rework mmap_exit vs. oom_reaper synchronization
> mm, oom: keep retrying the oom_reap operation as long as there is substantial memory left
> mm, oom: hand over MMF_OOM_SKIP to exit path if it is guranteed to finish
>
> Diffstat:
> include/linux/oom.h | 2 --
> mm/internal.h | 3 +++
> mm/memory.c | 28 ++++++++++++++--------
> mm/mmap.c | 69 +++++++++++++++++++++++++++++++++--------------------
> mm/oom_kill.c | 45 ++++++++++++++++++++++++----------
> 5 files changed, 97 insertions(+), 50 deletions(-)
>
> [1] http://lkml.kernel.org/r/20180910125513.311-1-mhocko@kernel.org
>

--
Michal Hocko
SUSE Labs

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