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[36.225.97.241]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b5fab0cdc6sm143067325ad.46.2026.04.21.18.23.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2026 18:23:35 -0700 (PDT) Date: Wed, 22 Apr 2026 09:23:31 +0800 From: Cheng-Yang Chou To: Tejun Heo Cc: void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, sched-ext@lists.linux.dev, emil@etsalapatis.com, linux-kernel@vger.kernel.org, Ching-Chun Huang , Chia-Ping Tsai Subject: Re: [PATCHSET sched_ext/for-7.2] sched_ext: Topological CPU IDs and cid-form struct_ops Message-ID: <20260422090721.G2bdb@cchengyang.duckdns.org> References: <20260421071945.3110084-1-tj@kernel.org> <20260422015408.Gac88@cchengyang.duckdns.org> <366940a49ecc5307db2654c49b137a4a@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <366940a49ecc5307db2654c49b137a4a@kernel.org> Hi Tejun, On Tue, Apr 21, 2026 at 08:33:51AM -1000, Tejun Heo wrote: > > 1. Regarding the ext_cid feature (same as ext_idle), is it feasible to > > implement this within the BPF arena instead of the current approach? > > No - cid-form struct_ops translates cids <-> cpus at the ops boundary, > so the kernel needs direct access to the mapping. Building it also > pulls from cpu_to_node() / cacheinfo / sibling masks which aren't > reachable from BPF. I see. Thanks for the details. (I was wondering if there might be an opportunity to contribute here, but it sounds non-trivial. I'll just keep it in mind for now.) > > > 2. I noticed rust/kernel/cpumask.rs is already in tree. ... would it be > > a good time to start adding Rust abstractions ... > > I'd wait for a concrete in-tree consumer before growing Rust > wrappers speculatively. Agreed, it's definitely too early for that. Should we also update the doc? Perhaps adding a dedicated 'Topological CPU IDs (cids)' section would be better than just a one-liner. Also, is there a need for a standalone selftest? I noticed scx_qmap already utilizes ext_cid, so I wasn't sure if a separate test is required. Happy to help with either, thanks! -- Cheers, Cheng-Yang