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Mon, 24 Apr 2023 21:11:54 -0400 X-MC-Unique: gTPKl2caMkCpdgS6BrP0TA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CF42A3847082; Tue, 25 Apr 2023 01:11:53 +0000 (UTC) Received: from localhost (ovpn-13-210.pek2.redhat.com [10.72.13.210]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 22A4440C6E67; Tue, 25 Apr 2023 01:11:52 +0000 (UTC) Date: Tue, 25 Apr 2023 09:11:47 +0800 From: Baoquan He To: Lorenzo Stoakes , Uladzislau Rezki , Michal Hocko Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org Subject: Re: [Lsf-pc] LSFMMBPF proposal [MM]: Eliminate vmap/vmalloc lock contention Message-ID: References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 56E59180010 X-Stat-Signature: 85dwyq7oqjcgs1iebxirbtepbdp3frps X-HE-Tag: 1682385118-954211 X-HE-Meta: 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 URWcLDCJ 310n/tJbIZGxCcGkH5ooGU1E1lK8dZTnLrR1FCJ0SDsQKuxCtSBlx8Kbm2RyXRr20WpEsIi50H/47HaBzqw6FIJkMn6HtVqB4r7bYmtucDMi/Qpg0SIX4SeN1I0JypbORl3LWl0fLsb+vM4xpqhjN9J/F/S4wJb8OIqswc+UtEBbYffR1D7d274l6Ie4p28u5jZv7iK9VanE4dfjyYQXGm3E8EGSUPgUuPByGVkKUROuil/0+qJuqhOgqufatQaewidiC X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 04/24/23 at 11:22am, Lorenzo Stoakes wrote: > On Mon, Apr 24, 2023 at 12:08:22PM +0200, Uladzislau Rezki wrote: > > On Mon, Apr 24, 2023 at 10:55:20AM +0200, Michal Hocko wrote: > > > On Mon 24-04-23 09:44:00, Uladzislau Rezki wrote: > > > > On Fri, Apr 21, 2023 at 02:03:43PM +0200, Michal Hocko wrote: > > > > > On Tue 28-02-23 17:42:43, Uladzislau Rezki wrote: > > > > > > Hello, LSF. > > > > > > > > > > > > Title: Introduce a per-cpu-vmap-cache to eliminate a vmap lock contention > > > > > > > > > > > > Description: > > > > > > Currently the vmap code is not scaled to number of CPU cores in a system > > > > > > because a global vmap space is protected by a single spinlock. Such approach > > > > > > has a clear bottleneck if many CPUs simultaneously access to one resource. > > > > > > > > > > > > In this talk i would like to describe a drawback, show some data related > > > > > > to contentions and places where those occur in a code. Apart of that i > > > > > > would like to share ideas how to eliminate it providing a few approaches > > > > > > and compare them. > > > > > > > > > > It's been some time since you brough this up. Has there been any > > > > > progress on the topic? Do you still find it important to discuss it at > > > > > LSFMM? > > > > > > > > > The idea about sequence was/is: > > > > > > > > 1) Give an overview on the proposal; > > > > 2) Submit patches to address the problem; > > > > 3) Start a discussion over lkml with people who are interested in it; > > > > 4) Send out a complete solution. > > > > > > Thanks for the clarification. The usual LSFMM format is strongly > > > discussion focused. Long presentations are usually discouraged and they > > > should only introduce people to the underlying problem to kick of a > > > discussion. > > > > > I have not posted yet any RFC and have not kicked it yet. Though people > > are aware the problem. > > > > > > > > That being said, IMO it would be helpful to have some material on the > > > mailing list before any discussion could be productive. > > > > > This is what i have so far: > > > > wget ftp://vps418301.ovh.net/incoming/Fix_a_vmalloc_lock_contention_in_SMP_env.pdf > > > > I can, of course, move it forward over lkml only. If you are fully > > booked or there other reason then please just withdraw my proposal > > from your conference. > > For what it's worth I'm definitely interested in attending this session if > it goes ahead. I am sure Baoquan, if he's attending LSF/MM, would be too! (cc'd). Thanks for CC. Yes, I am very interested in this topic, have read it from the beginning. Unfortunately, I can't attend LSF/MM this year because of some reasons. I look forward to learning the decision or conclusion of the sessin, and reviewing Uladzislau's RFC or formal patchset later. Wish the session a great success, and you guys a pleasant meeting and discussion. Thanks Baoquan