From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Jan Kara <jack@suse.cz>
Cc: Gabriel Krisman Bertazi <krisman@suse.de>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Mateusz Guzik <mjguzik@gmail.com>,
Shakeel Butt <shakeel.butt@linux.dev>,
Michal Hocko <mhocko@kernel.org>, Dennis Zhou <dennis@kernel.org>,
Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@gentwo.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
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>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 0/4] Optimize rss_stat initialization/teardown for single-threaded tasks
Date: Fri, 28 Nov 2025 15:12:25 -0500 [thread overview]
Message-ID: <bcc7140f-5efb-481c-b1e9-564a2d88ed81@efficios.com> (raw)
In-Reply-To: <yvghqmbugs3oejsvbh5rrw76rvtr2wfwqysjd7tw67z4tzpdbp@6zehhuzumiez>
On 2025-11-28 15:10, Jan Kara wrote:
> On Fri 28-11-25 08:30:08, Mathieu Desnoyers wrote:
[...]
>> I suspect that by doing just that we'd get most of the
>> performance benefits provided by the single-threaded special-case
>> proposed here.
>
> I don't think so. Because in the profiles I have been doing for these
> loads the biggest cost wasn't actually the per-cpu allocation itself but
> the cost of zeroing the allocated counter for many CPUs (and then the
> counter summarization on exit) and you're not going to get rid of that with
> just reshuffling per-cpu fields and adding slab allocator in front.
That's a good point ! So skipping the zeroing of per-cpu fields would
indeed justify special-casing the single-threaded case.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
next prev parent reply other threads:[~2025-11-28 20:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-27 23:36 Gabriel Krisman Bertazi
2025-11-27 23:36 ` [RFC PATCH 1/4] lib/percpu_counter: Split out a helper to insert into hotplug list Gabriel Krisman Bertazi
2025-11-27 23:36 ` [RFC PATCH 2/4] lib: Support lazy initialization of per-cpu counters Gabriel Krisman Bertazi
2025-11-27 23:36 ` [RFC PATCH 3/4] mm: Avoid percpu MM counters on single-threaded tasks Gabriel Krisman Bertazi
2025-11-27 23:36 ` [RFC PATCH 4/4] mm: Split a slow path for updating mm counters Gabriel Krisman Bertazi
2025-12-01 10:19 ` David Hildenbrand (Red Hat)
2025-11-28 13:30 ` [RFC PATCH 0/4] Optimize rss_stat initialization/teardown for single-threaded tasks Mathieu Desnoyers
2025-11-28 20:10 ` Jan Kara
2025-11-28 20:12 ` Mathieu Desnoyers [this message]
2025-11-29 5:57 ` Mateusz Guzik
2025-11-29 7:50 ` Mateusz Guzik
2025-12-01 10:38 ` Harry Yoo
2025-12-01 11:31 ` Mateusz Guzik
2025-12-01 14:47 ` Mathieu Desnoyers
2025-12-01 15:23 ` Gabriel Krisman Bertazi
2025-12-01 19:16 ` Harry Yoo
2025-12-03 11:02 ` Mateusz Guzik
2025-12-03 11:54 ` Mateusz Guzik
2025-12-03 14:36 ` Mateusz Guzik
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