linux-kernel - Re: [PATCH v7 2/2] mm/oom_kill: The OOM reaper traverses the VMA maple tree in reverse order

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Message-ID: <a3hgvhvix2ulzfof6d23f7kzk5clsnea3grmd2wowjyhjwuiyn@ymzvkqf7gcsc>
Date: Thu, 4 Sep 2025 22:12:48 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Michal Hocko <mhocko@...e.com>
Cc: zhongjinji <zhongjinji@...or.com>, rientjes@...gle.com,
        shakeel.butt@...ux.dev, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        lorenzo.stoakes@...cle.com, surenb@...gle.com, liulu.liu@...or.com,
        feng.han@...or.com
Subject: Re: [PATCH v7 2/2] mm/oom_kill: The OOM reaper traverses the VMA
 maple tree in reverse order

* Michal Hocko <mhocko@...e.com> [250904 08:21]:
> On Wed 03-09-25 15:02:34, Liam R. Howlett wrote:
> > * Michal Hocko <mhocko@...e.com> [250903 08:58]:
> > > On Wed 03-09-25 17:27:29, zhongjinji wrote:
> [...]
> > mmu_notifier_release(mm) is called early in the exit_mmap() path should
> > cause the mmu notifiers to be non-blocking (according to the comment in
> > v6.0 source of exit_mmap [1].
> 
> I am not sure I follow you here. How does this relate to the actual
> direction of the address space freeing?

It doesn't relate to the direction of the address freeing, I think it
explains the perf data a bit.

The exit_mmap() would have a decrease in mmu related work while this
thread will have an increase, I think.

If they race, this thread gets virtually nothing while exit does all of
the work.  If they don't race then the work is split.

Does that make sense?

Thanks,
Liam