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[141.239.159.203]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f9eb2f037fsm17473825ad.59.2024.06.21.12.10.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Jun 2024 12:10:03 -0700 (PDT) Date: Fri, 21 Jun 2024 09:10:02 -1000 From: Tejun Heo To: David Rientjes Cc: Andrew Morton , "Liam R. Howlett" , Suren Baghdasaryan , Matthew Wilcox , Christoph Lameter , "Paul E. McKenney" , Johannes Weiner , Davidlohr Bueso , Namhyung Kim , linux-mm@kvack.org Subject: Re: MM global locks as core counts quadruple Message-ID: References: <07e7d078-0c9d-6a1f-1ab5-295f86974b72@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07e7d078-0c9d-6a1f-1ab5-295f86974b72@google.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 035C74000C X-Stat-Signature: jj7hc36q84ouikkyhrbd7yi7tt94p354 X-Rspam-User: X-HE-Tag: 1718997004-783090 X-HE-Meta: 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 rbu7tdI8 VqMdyUu1qa1C/1YucjwZ+4kQ96Y4ARytbTtJOc2gCe/q/XAqFPbWGSbVwoOvw9iLRIBxsYS7uCIXDr+4drySucilGRWrcZQ3UfJfpJymjrq1bKlAuKJJfJ0dl8V9p/y+H0z3MiVhdcCnNKsYpEY1kQCdzib11Qgjclr5mF5dgh408KZI4F43+ovLmLtVYHR4jmunoQshOR851L7RFnvik4TifsOIx6PiSm/iEgijyuZnISoq/4URddGYsc/I4pP6eNZNZ4MNvHTck1ukEKd0mhxGJIqp4qYSVeFq55OEAwE5MkLZSCj1GCh5d+vUJzZhzBJvepELt5qe8aRz578PZRsxy5sxiZR+sVIxK5Hy6dki2xBJa5Eer3I3MkYVx+R5N/laaXVdbhC/nBkuU9LJjfUQ0cVaHQ1a8omUIHWR/IJdxamREJMYzLin72Eg/dyVmmC46 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: List-Subscribe: List-Unsubscribe: Hello, On Thu, Jun 20, 2024 at 05:35:45PM -0700, David Rientjes wrote: > As core counts are rapidly expanding over the next four years, Namhyung > and I were looking at global locks that we're already seeing high > contention on even today. > > Some of these are not MM specific: > - cgroup_mutex Our machines are getting bigger but we aren't creating and destroying cgroups frequently enough for this to matter. But yeah, I can see how this can be a problem. > - cgroup_threadgroup_rwsem This one shouldn't matter at all in setups where new cgroups are populated with CLONE_INTO_CGROUP and not migrated further. The lock isn't grabbed in such usage pattern, which should be the vast majority already, I think. Are you guys migrating tasks a lot or not using CLONE_INTO_CGROUP? Thanks. -- tejun