From: Suren Baghdasaryan <surenb@google.com>
To: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Matthew Wilcox <willy@infradead.org>,
Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
Minchan Kim <minchan@kernel.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Andrea Arcangeli <aarcange@redhat.com>,
Christian Brauner <christian@brauner.io>,
Christoph Hellwig <hch@infradead.org>,
Oleg Nesterov <oleg@redhat.com>,
David Hildenbrand <david@redhat.com>,
Jann Horn <jannh@google.com>, Shakeel Butt <shakeelb@google.com>,
Andy Lutomirski <luto@kernel.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
Florian Weimer <fweimer@redhat.com>,
Jan Engelhardt <jengelh@inai.de>,
Tim Murray <timmurray@google.com>,
Vlastimil Babka <vbabka@suse.cz>, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@android.com>
Subject: Re: [PATCH 4/3] mm: drop MMF_OOM_SKIP from exit_mmap
Date: Tue, 4 Jan 2022 14:24:50 -0800 [thread overview]
Message-ID: <CAJuCfpFm-4GSu4D_tWMV0a08LNVLjksEnRgRfaYvbciK=wCScA@mail.gmail.com> (raw)
In-Reply-To: <35c340a6-96f-28a0-2b7b-2f9fbddc01f@google.com>
On Mon, Jan 3, 2022 at 1:16 PM Hugh Dickins <hughd@google.com> wrote:
>
> On Mon, 3 Jan 2022, Michal Hocko wrote:
> > On Thu 30-12-21 09:29:40, Suren Baghdasaryan wrote:
> > > On Thu, Dec 30, 2021 at 12:24 AM Michal Hocko <mhocko@suse.com> wrote:
> > > >
> > > > It would be really great to make unlock_range oom reaper aware IMHO.
> > >
> > > What exactly do you envision? Say unlock_range() knows that it's
> > > racing with __oom_reap_task_mm() and that calling follow_page() is
> > > unsafe without locking, what should it do?
> >
> > My original plan was to make the page lock conditional and use
> > trylocking from the oom reaper (aka lockless context). It is OK to
> > simply bail out and leave some mlocked memory behind if there is a
> > contention on a specific page. The overall objective is to free as much
> > memory as possible, not all of it.
> >
> > IIRC Hugh was not a fan of this approach and he has mentioned that the
> > lock might not be even really needed and that the area would benefit
> > from a clean up rather than oom reaper specific hacks. I do tend to
> > agree with that. I just never managed to find any spare time for that
> > though and heavily mlocked oom victims tend to be really rare.
>
> I forget when that was, and what I had in mind at that time.
> But yes, by now I am very sure that munlocking needs a cleanup.
>
> And I do have that cleanup (against a much older tree), but never
> the time to rebase or post or shepherd it through N revisions.
How old was that tree?
>
> It was 22 files changed, 464 insertions, 706 deletions:
> which is too much to help with this immediate oom reaper question.
>
> I'd better not drive this discussion further off-course; but it pains
> me to see munlock_vma_pages obstructing, knowing there's a better way.
>
> I wonder: what if I were to steal time and promise to post a
> rebased series against 5.17-rc1 or rc2: not support it thereafter,
> but might there be someone to pick it up and shepherd it through?
> But there's no answer to that, without you seeing what it's like.
I would be interested in taking a look and see if it can be upstreamed
and supported without bugging you too much.
Thanks,
Suren.
>
> Hugh
prev parent reply other threads:[~2022-01-04 22:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 21:22 [PATCH v4 1/3] mm: protect free_pgtables with mmap_lock write lock in exit_mmap Suren Baghdasaryan
2021-12-08 21:22 ` [PATCH v4 2/3] mm: document locking restrictions for vm_operations_struct::close Suren Baghdasaryan
2021-12-09 8:55 ` Michal Hocko
2021-12-08 21:22 ` [PATCH v4 3/3] mm/oom_kill: allow process_mrelease to run under mmap_lock protection Suren Baghdasaryan
2021-12-09 8:59 ` Michal Hocko
2021-12-09 19:03 ` Suren Baghdasaryan
2021-12-09 8:55 ` [PATCH v4 1/3] mm: protect free_pgtables with mmap_lock write lock in exit_mmap Michal Hocko
2021-12-09 19:03 ` Suren Baghdasaryan
2021-12-10 9:20 ` Michal Hocko
2021-12-09 9:12 ` [PATCH 4/3] mm: drop MMF_OOM_SKIP from exit_mmap Michal Hocko
2021-12-09 16:24 ` Suren Baghdasaryan
2021-12-09 16:47 ` Michal Hocko
2021-12-09 17:06 ` Suren Baghdasaryan
2021-12-16 2:26 ` Suren Baghdasaryan
2021-12-16 11:49 ` Johannes Weiner
2021-12-16 17:23 ` Suren Baghdasaryan
2021-12-30 5:59 ` Suren Baghdasaryan
2021-12-30 8:24 ` Michal Hocko
2021-12-30 17:29 ` Suren Baghdasaryan
2022-01-03 12:11 ` Michal Hocko
2022-01-03 21:16 ` Hugh Dickins
2022-01-04 22:24 ` Suren Baghdasaryan [this message]
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