Messages in this thread Patch in this message | | | From | Nico Pache <> | Subject | [RFC 3/3] exit: Check for MMF_OOM_SKIP in exit_mmap | Date | Thu, 21 Apr 2022 15:05:33 -0400 |
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The MMF_OOM_SKIP bit is used to indicate weather a mm_struct can not be invalided or has already been invalided. exit_mmap currently calls __oom_reap_task_mm unconditionally despite the fact that the oom reaper may have already called this.
Add a check for the MMF_OOM_SKIP bit being set in exit_mmap to avoid unnessary calls to the invalidate code.
A slight race can occur on the MMF_OOM_SKIP bit that will still allow this to run twice. My testing has shown an ~66% decrease in double calls to _oom_reap_task_mm.
Fixes: 27ae357fa82b ("mm, oom: fix concurrent munlock and oom reaper unmap, v3") Cc: David Rientjes <rientjes@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Nico Pache <npache@redhat.com> --- mm/mmap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/mmap.c b/mm/mmap.c index a2968669fd4e..b867f408dacd 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3113,7 +3113,8 @@ void exit_mmap(struct mm_struct *mm) /* mm's last user has gone, and its about to be pulled down */ mmu_notifier_release(mm); - if (unlikely(mm_is_oom_victim(mm))) { + if (unlikely(mm_is_oom_victim(mm)) && + !test_bit(MMF_OOM_SKIP, &mm->flags)) { /* * Manually reap the mm to free as much memory as possible. * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard -- 2.35.1
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