From: Matthew Wilcox <willy@infradead.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: David Hildenbrand <david@redhat.com>,
akpm@linux-foundation.org, jirislaby@kernel.org,
jacobly.alt@gmail.com, holger@applied-asynchrony.com,
michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
dave@stgolabs.net, liam.howlett@oracle.com, peterz@infradead.org,
ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com,
will@kernel.org, luto@kernel.org, songliubraving@fb.com,
peterx@redhat.com, dhowells@redhat.com, hughd@google.com,
bigeasy@linutronix.de, kent.overstreet@linux.dev,
punit.agrawal@bytedance.com, lstoakes@gmail.com,
peterjung1337@gmail.com, rientjes@google.com,
chriscli@google.com, axelrasmussen@google.com, joelaf@google.com,
minchan@google.com, rppt@kernel.org, jannh@google.com,
shakeelb@google.com, tatashin@google.com, edumazet@google.com,
gthelen@google.com, linux-mm@kvack.org
Subject: Re: [PATCH 1/1] mm: disable CONFIG_PER_VMA_LOCK by default until its fixed
Date: Tue, 4 Jul 2023 18:55:45 +0100 [thread overview]
Message-ID: <ZKRdIUo0crrfnly4@casper.infradead.org> (raw)
In-Reply-To: <CAJuCfpHq7tXjJCExO96P5dVWrFaZrLOacoG3yjduEsF_Qy4MUg@mail.gmail.com>
On Tue, Jul 04, 2023 at 10:21:12AM -0700, Suren Baghdasaryan wrote:
> On Tue, Jul 4, 2023 at 6:07 AM Matthew Wilcox <willy@infradead.org> wrote:
> > Calling fork() from a multi-threaded program is fraught with danger.
> > It's a rare thing to do, and we don't need to optimise for it. It
> > does, of course, need to not crash. But we can slow it down as much as
> > we want to. Slowing down single-threaded programs calling fork is
> > much less acceptable.
>
> Hmm. Would you suggest we use different approaches for multi-threaded
> vs single-threaded programs?
> I think locking VMAs while forking a process which has lots of VMAs
> will regress by some amount (we are adding non-zero work). The
> question is if that's acceptable or we have to implement something
> different. I verified that solution fixes the issue shown by the
> reproducer, now I'm trying to quantify this fork performance
> regression I suspect we will introduce.
It might make sense to do that. Personally, I'd try to quantify it
with a make -jN build of the kernel. That workload is fork-heavy of
single threaded processes, and if it doesn't show much difference, I think
we're good.
next prev parent reply other threads:[~2023-07-04 17:56 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 18:21 [PATCH 1/1] mm: disable CONFIG_PER_VMA_LOCK by default until its fixed Suren Baghdasaryan
2023-07-03 20:07 ` David Rientjes
2023-07-03 20:30 ` David Hildenbrand
2023-07-04 5:39 ` Suren Baghdasaryan
2023-07-04 6:50 ` Suren Baghdasaryan
2023-07-04 7:18 ` David Hildenbrand
2023-07-04 7:34 ` Suren Baghdasaryan
2023-07-04 8:03 ` David Hildenbrand
2023-07-04 18:01 ` David Hildenbrand
2023-07-04 13:07 ` Matthew Wilcox
2023-07-04 17:21 ` Suren Baghdasaryan
2023-07-04 17:36 ` David Hildenbrand
2023-07-04 17:56 ` Suren Baghdasaryan
2023-07-04 18:05 ` David Hildenbrand
2023-07-04 19:11 ` Suren Baghdasaryan
2023-07-04 20:10 ` Suren Baghdasaryan
[not found] ` <7d6ba07b-ee60-8920-b91c-04c826eb4690@applied-asynchrony.com>
2023-07-04 22:03 ` Suren Baghdasaryan
2023-07-04 22:42 ` Matthew Wilcox
[not found] ` <a7149847-4b53-8ff0-d570-042631a1ce20@applied-asynchrony.com>
2023-07-05 6:46 ` Suren Baghdasaryan
2023-07-04 17:55 ` Matthew Wilcox [this message]
2023-07-04 17:58 ` Suren Baghdasaryan
2023-07-04 8:12 ` Linux regression tracking (Thorsten Leemhuis)
2023-07-04 8:30 ` Hans de Goede
2023-07-04 8:18 ` Hans de Goede
2023-07-04 15:24 ` Suren Baghdasaryan
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