From: Michal Hocko <mhocko@suse.com>
To: Nico Pache <npache@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
David Rientjes <rientjes@google.com>,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [RFC 3/3] exit: Check for MMF_OOM_SKIP in exit_mmap
Date: Fri, 22 Apr 2022 17:38:44 +0200 [thread overview]
Message-ID: <YmLMBDkHmcjf9Nem@dhcp22.suse.cz> (raw)
In-Reply-To: <20220421190533.1601879-4-npache@redhat.com>
On Thu 21-04-22 15:05:33, Nico Pache wrote:
> 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.
Why do we care about this?
> 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")
I do not see this would be fixing anything.
> 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
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2022-04-22 15:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-21 19:05 [RFC 0/3] Slight improvements for OOM/Futex Nico Pache
2022-04-21 19:05 ` [RFC 1/3] mm: change vma_is_anonymous to vma_is_private_anon Nico Pache
2022-04-21 19:28 ` Matthew Wilcox
2022-04-22 14:00 ` Nico Pache
2022-04-28 16:14 ` David Hildenbrand
2022-04-21 19:05 ` [RFC 2/3] futex: exit: Print a warning when futex_cleanup fails Nico Pache
2022-04-21 19:30 ` Matthew Wilcox
2022-04-22 14:12 ` Nico Pache
2022-04-21 20:53 ` Thomas Gleixner
2022-04-22 14:23 ` Nico Pache
2022-04-22 14:42 ` Thomas Gleixner
2022-04-21 19:05 ` [RFC 3/3] exit: Check for MMF_OOM_SKIP in exit_mmap Nico Pache
2022-04-22 15:38 ` Michal Hocko [this message]
2022-04-25 19:00 ` Nico Pache
2022-04-26 6:59 ` Michal Hocko
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