From: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Matthew Wilcox <willy@infradead.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
Minchan Kim <minchan@kernel.org>,
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>,
Linux API <linux-api@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team <kernel-team@android.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 1/1] mm: prevent a race between process_mrelease and exit_mmap
Date: Tue, 2 Nov 2021 08:14:43 -0700 [thread overview]
Message-ID: <CAJuCfpFX8FRynoK29h8tpRXRT-Kk+sHboiBnc7N-8MY6AAqVLw@mail.gmail.com> (raw)
In-Reply-To: <YYDvm9c/7cGtBvw6@dhcp22.suse.cz>
On Tue, Nov 2, 2021 at 12:58 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Mon 01-11-21 08:44:58, Suren Baghdasaryan wrote:
> [...]
> > I'm with you on this one, that's why I wanted to measure the price we
> > would pay. Below are the test results:
> >
> > Test: https://lore.kernel.org/all/20170725142626.GJ26723@dhcp22.suse.cz/
> > Compiled: gcc -O2 -static test.c -o test
> > Test machine: 128 core / 256 thread 2x AMD EPYC 7B12 64-Core Processor
> > (family 17h)
> >
> > baseline (Linus master, f31531e55495ca3746fb895ffdf73586be8259fa)
> > p50 (median) 87412
> > p95 168210
> > p99 190058
> > average 97843.8
> > stdev 29.85%
> >
> > unconditional mmap_write_lock in exit_mmap (last column is the change
> > from the baseline)
> > p50 (median) 88312 +1.03%
> > p95 170797 +1.54%
> > p99 191813 +0.92%
> > average 97659.5 -0.19%
> > stdev 32.41%
> >
> > unconditional mmap_write_lock in exit_mmap + Matthew's patch (last
> > column is the change from the baseline)
> > p50 (median) 88807 +1.60%
> > p95 167783 -0.25%
> > p99 187853 -1.16%
> > average 97491.4 -0.36%
> > stdev 30.61%
> >
> > stdev is quite high in all cases, so the test is very noisy.
> > The impact seems quite low IMHO. WDYT?
>
> Results being very noisy is what I recall as well. Thanks!
I believe, despite the noise, the percentiles show that overall we do
not noticeably regress the exit path by taking mmap_lock
unconditionally.
If there are no objections, I would like to post a patchset which
implements unconditional locking in exit_mmap() and process_madvise()
calling __oom_reap_task_mm() under protection of read mmap_lock.
Thanks!
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2021-11-02 15:14 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-22 1:46 [PATCH 1/1] mm: prevent a race between process_mrelease and exit_mmap Suren Baghdasaryan
2021-10-22 2:24 ` Andrew Morton
2021-10-22 5:23 ` Suren Baghdasaryan
2021-10-22 8:03 ` Michal Hocko
2021-10-22 11:32 ` Matthew Wilcox
2021-10-22 12:04 ` Michal Hocko
2021-10-22 17:38 ` Suren Baghdasaryan
2021-10-27 16:08 ` Suren Baghdasaryan
2021-10-27 17:33 ` Matthew Wilcox
2021-10-27 17:42 ` Suren Baghdasaryan
2021-10-27 17:51 ` Matthew Wilcox
2021-10-27 18:00 ` Suren Baghdasaryan
2021-10-29 13:03 ` Michal Hocko
2021-10-29 16:07 ` Suren Baghdasaryan
2021-11-01 8:37 ` Michal Hocko
2021-11-01 15:44 ` Suren Baghdasaryan
2021-11-01 19:59 ` Suren Baghdasaryan
2021-11-02 7:58 ` Michal Hocko
2021-11-02 15:14 ` Suren Baghdasaryan [this message]
2021-11-09 19:01 ` Suren Baghdasaryan
2021-11-09 19:26 ` Michal Hocko
2021-11-09 19:37 ` Suren Baghdasaryan
2021-11-09 19:50 ` Michal Hocko
2021-11-09 20:02 ` Suren Baghdasaryan
2021-11-09 20:10 ` Michal Hocko
2021-11-09 21:10 ` Suren Baghdasaryan
2021-11-11 1:49 ` Suren Baghdasaryan
2021-11-11 9:20 ` Michal Hocko
2021-11-11 15:02 ` Suren Baghdasaryan
2021-11-12 8:58 ` Michal Hocko
2021-11-12 16:00 ` Suren Baghdasaryan
2021-11-09 19:41 ` Michal Hocko
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