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Wed, 04 Nov 2026 16:38:52 -0800 (PST) Received: from WindFlash.powerhub ([2a0a:ef40:f61:3b01:d08a:833b:756:8fce]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fed553441sm5988761f8f.43.2026.11.04.16.38.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 16:38:51 -0800 (PST) From: Leonardo Bras To: Frederic Weisbecker Cc: Leonardo Bras , Matthew Ruffell , Waiman Long , Tejun Heo , Peter Zijlstra , Ingo Molnar , Andrew Morton , David Hildenbrand , Caron Wills , Ridong Chen , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Jay Vosburgh Subject: Re: [PATCH 4/6] sched/isolation: Drain per-CPU LRU batches when CPUs become isolated Date: Wed, 4 Nov 2026 21:38:50 -0300 Message-ID: X-Mailer: git-send-email 2.55.0 In-Reply-To: References: <20261103075940.110308-1-matthew.ruffell@canonical.com> <20261103075940.110308-5-matthew.ruffell@canonical.com> X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Tue, Nov 03, 2026 at 03:10:22PM +0100, Frederic Weisbecker wrote: > Le Tue, Nov 03, 2026 at 08:59:38PM +1300, Matthew Ruffell a écrit : > > From: Caron Wills > > > > Isolated CPUs no longer batch folios in their per-CPU LRU caches, so > > that __lru_add_drain_all() never has to queue work on them. Boot time > > isolation (isolcpus=, nohz_full=) takes effect before any folio is > > batched, but a cpuset isolated partition can be created at runtime and > > the affected CPUs may still hold folios in their batches from before. > > Those would linger until the CPU happens to drain locally, and the next > > lru_add_drain_all() would fall back to queueing work on the now isolated > > CPU, which is exactly what must be avoided. > > > > Drain all batches once from housekeeping_update(), right after the > > HK_TYPE_DOMAIN mask has been updated and next to the vmstat and memcg > > workqueue flushes that exist for the same reason, so that newly isolated > > CPUs start out with empty batches. > > > > Link: https://bugs.launchpad.net/bugs/2165410 > > Signed-off-by: Caron Wills > > Signed-off-by: Matthew Ruffell > > There was this patchset: > https://lore.kernel.org/lkml/20260519012754.240804-1-leobras.c@gmail.com/ > > Leonardo, do you plan a v5? Yeah, working on that. Hopefully should be tested by the end of this month. Thanks! Leo