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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93ef502608bsm483806485a.25.2026.10.14.05.35.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Oct 2026 05:35:12 -0700 (PDT) Date: Wed, 14 Oct 2026 08:35:09 -0400 From: Gregory Price To: Yafang Shao Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, david@kernel.org, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, shakeel.butt@linux.dev, roman.gushchin@linux.dev, yu.c.chen@intel.com, zhao1.liu@intel.com, bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 0/3] BPF-based per-cgroup NUMA balancing mode selection Message-ID: References: <20261012120438.52849-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 68BE218000D X-Rspam-User: X-Stat-Signature: oj6o5npf1bokub7haksrgi36kbmjdscc X-HE-Tag: 1791981313-843220 X-HE-Meta: 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 ZzlUFygQ xWTqbS6JAg6BQoLCeipIJtoscya2eDOv9DLCiWI7U2b4Rgd6hOb8LbYS5fAqo41jrKQxOXF1Jp6MjxHMXAHAYbEQBQgZnt5npmecm+6dpocn4L8KroHOPbFb0R9Xv76AcTXfvjOEPk6bvdfAd8aq/50lKbnxnn7dnmdu5b0evNZOB6QACBwXTpmgYrKrYvRB/GgoByyCVc+4mj0GdfNco9Rg9YGHrNmDV0BKX5QENdVgRIvwGryM9MpWJxkQe9SANcmeuONBnER3OPUQYh4dmhHNzbNWqQ6cdEvaJDRU7+NLB6hVgACz7GL4hv1DdBrunoy13LRIz9slRQnhHxy0iEdR4HKYEyp6YC22xiY78OFviDc4UZu10h8QfAe/7X18Kglk5PBiWmOefBXp0GeKPuFucFw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Oct 14, 2026 at 11:08:40AM +0800, Yafang Shao wrote: > > > > I also concur with Tejun that ops seems like overkill for this feature, > > this seems like something that can already be managed. > > Tejun also suggested starting with a smaller kfunc rather than the > heavyweight struct_ops, in a separate mailing list thread. I agree > that this would be a good starting point. > > > > > For example, why not add a new numa balancing mode bit that says > > "enabled but only for explicitly opted in tasks" and then ignore the > > global default mempolicy, e.g.: > > > > if (numab_mode & NUMA_BALANCING_OPT_IN && > > mpol != default && > > mpol.flags & MPOL_F_NUMA_BALANCING) > > /* do balancing */ > > Another option would be to add a cgroup::numab_mode field (without > exposing a cgroupfs interface file for now) to implement per-cgroup > numab mode. I will think it over, considering both your suggestion and > Tejun's. > I don't have a strong feeling either way, if Tejun thinks a kfunc is acceptable here then that's probably preferable to any new UAPI changes until the value is proven. Thank you for the consideration, ~Gregory