From: Linus Walleij <linusw@kernel.org>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Kees Cook <kees@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
linux-mm@kvack.org, Mateusz Guzik <mjguzik@gmail.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: Re: [PATCH] fork: zero vmap stack using clear_pages() instead of memset()
Date: Tue, 24 Feb 2026 14:53:23 +0100 [thread overview]
Message-ID: <CAD++jLm6iyeFuGoC2zfHDOu6gYdb2L1gsjQhT5a4qS-CBWia9Q@mail.gmail.com> (raw)
In-Reply-To: <2553a75a-6dc8-4295-96b3-58367879751c@kernel.org>
On Tue, Feb 24, 2026 at 2:21 PM David Hildenbrand (Arm)
<david@kernel.org> wrote:
> On 2/24/26 11:26, Linus Walleij wrote:
> > After the introduction of clear_pages() we exploit the
> > fact that the process vm_area is allocated in contiguous
> > pages to just clear them all in one swift operation.
>
> The pages are virtually contiguous (vmalloc IIUC), not necessarily
> physically contiguous. For clear_pages() that should work.
Yeah that's what I meant with contiguous, sorry.
> > /* Clear stale pointers from reused stack. */
> > - memset(stack, 0, THREAD_SIZE);
> > + clear_pages(vm_area->addr, vm_area->nr_pages);
>
> LGTM.
>
> Do we have any idea about performance impact etc?
I have a pending patch for implementing clear_pages() for arm64,
https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-integrator.git/log/?h=b4/aarch64-clear-pages
which is in a performance test loop, once I get baseline data from that
I can test something fork-intensive (hackbench, I guess) with this patch on top.
So making that patch made me remember this one code site...
If someone has a good fork performance test running on x86
and can give this a spin, it'd be great!
Yours,
Linus Walleij
next prev parent reply other threads:[~2026-02-24 13:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-24 10:26 Linus Walleij
2026-02-24 13:21 ` David Hildenbrand (Arm)
2026-02-24 13:53 ` Linus Walleij [this message]
2026-02-24 14:26 ` David Hildenbrand (Arm)
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