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Wed, 11 Mar 2026 11:06:22 -0700 (PDT) Date: Wed, 11 Mar 2026 14:06:18 -0400 From: Johannes Weiner To: "JP Kobryn (Meta)" Cc: Usama Arif , linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, apopple@nvidia.com, axelrasmussen@google.com, byungchul@sk.com, cgroups@vger.kernel.org, david@kernel.org, eperezma@redhat.com, gourry@gourry.net, jasowang@redhat.com, joshua.hahnjy@gmail.com, Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mst@redhat.com, rppt@kernel.org, muchun.song@linux.dev, zhengqi.arch@bytedance.com, rakie.kim@sk.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, surenb@google.com, virtualization@lists.linux.dev, weixugc@google.com, xuanzhuo@linux.alibaba.com, ying.huang@linux.alibaba.com, yuanchu@google.com, ziy@nvidia.com, kernel-team@meta.com Subject: Re: [PATCH v2] mm/mempolicy: track page allocations per mempolicy Message-ID: References: <20260308192438.1363382-1-usama.arif@linux.dev> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Sun, Mar 08, 2026 at 08:30:47PM -0700, JP Kobryn (Meta) wrote: > On 3/8/26 12:24 PM, Usama Arif wrote: > > On Fri, 6 Mar 2026 20:55:20 -0800 "JP Kobryn (Meta)" wrote: > [...] > >> +static void mpol_count_numa_alloc(struct mempolicy *pol, int intended_nid, > >> + struct page *page, unsigned int order) > >> +{ > >> + int actual_nid = page_to_nid(page); > >> + long nr_pages = 1L << order; > >> + enum node_stat_item hit_idx; > >> + struct mem_cgroup *memcg; > >> + struct lruvec *lruvec; > >> + bool is_hit; > >> + > >> + if (!root_mem_cgroup || mem_cgroup_disabled()) > >> + return; > > > > Hello JP! > > > > The stats are exposed via /proc/vmstat and are guarded by CONFIG_NUMA, not > > CONFIG_MEMCG. Early returning overhere would make it inaccuate. Does > > it make sense to use mod_node_page_state if memcg is not available, > > so that these global counters work regardless of cgroup configuration. > > > > Good call. I can instead do: > > if (!mem_cgroup_disabled() && root_mem_cgroup) { > struct mem_cgroup *memcg; > struct lruvec *lruvec; > /* use lruvec for updating stats */ > } else { > /* use node for updating stats */ > } > > This should also take care of the bot warning on mem_cgroup_from_task() > not being available. mem_cgroup_lruvec() and mod_lruvec_state() already do the right thing for !CONFIG_MEMCG. Add a dummy for mem_cgroup_from_task() and you can do a single, shared sequence for both configs.