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[109.81.94.244]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9061096694sm582699166b.19.2024.09.18.04.17.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Sep 2024 04:17:10 -0700 (PDT) Date: Wed, 18 Sep 2024 13:17:09 +0200 From: Michal Hocko To: Frederic Weisbecker Cc: LKML , Andrew Morton , Kees Cook , Peter Zijlstra , Thomas Gleixner , Vlastimil Babka , linux-mm@kvack.org, "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Boqun Feng , Zqiang , rcu@vger.kernel.org Subject: Re: [PATCH 12/19] kthread: Default affine kthread to its preferred NUMA node Message-ID: References: <20240916224925.20540-1-frederic@kernel.org> <20240916224925.20540-13-frederic@kernel.org> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed 18-09-24 11:37:42, Frederic Weisbecker wrote: > Le Tue, Sep 17, 2024 at 01:07:25PM +0200, Michal Hocko a écrit : [...] > > I am not objecting to patch per se. I am just not sure this is really > > needed. It is great to have kernel threads bound to non isolated cpus by > > default if they have node preferences. But as soon as somebody starts > > offlining cpus excessively and make the initial cpumask empty then > > select_fallback_rq sounds like the right thing to do. > > > > Not my call though. I was just curious why this is needed and it seems > > to me you are looking for some sort of correctness for broken setups. > > It looks like it makes sense to explore that path. We still need the > cpu up probe to reaffine when a suitable target comes up. But it seems > the CPU down part can be handled by select_fallback_rq. I'll try that. THanks! Btw. when you are looking at this, would it make sense to make select_fallback_rq more cpu isolation aware as well? I mean using housekeeping cpus before falling back to task_cpu_possible_mask? -- Michal Hocko SUSE Labs