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[34.125.132.248]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a2f3c87845sm214750925ad.39.2025.12.26.10.58.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Dec 2025 10:58:47 -0800 (PST) Date: Fri, 26 Dec 2025 18:58:42 +0000 From: Bing Jiao To: Chen Ridong Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, gourry@gourry.net, longman@redhat.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, tj@kernel.org, mkoutny@suse.com, david@kernel.org, zhengqi.arch@bytedance.com, lorenzo.stoakes@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, cgroups@vger.kernel.org Subject: Re: [PATCH v3] mm/vmscan: fix demotion targets checks in reclaim/demotion Message-ID: References: <20251221233635.3761887-1-bingjiao@google.com> <20251223212032.665731-1-bingjiao@google.com> <646ee1fa-edd1-4588-9720-c3c1df8ebce5@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <646ee1fa-edd1-4588-9720-c3c1df8ebce5@huaweicloud.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 20E38100006 X-Stat-Signature: aawzbdpdjd71hmepdyk74ahm34rt7tnz X-HE-Tag: 1766775529-29769 X-HE-Meta: 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 HeWc20H6 pmgPZjT1Flp6YipnXa9cdD0oxQslS4k637tasCPOLwjq7FrAf5IN0WYWYPYVFokvnRHcsbSMEhtzzM3Amvv3osH54xeaDwyBsCWodpVyZZSJ6BSj3awgm6AR5F4dtaS4JxLB0dwXBLmrk3nAhsgecnuxn1jt2TR4xguvEVBr79ml6Vgzm5qBROQ+iMnJVG3GdlreUKstnYsPwigk/2ROZOn9uQwu+i9cmeWe1o0ZXRODdjI2MDdSAGTIwfxvkTuF/xxJtuayLw1RQtrSxrUI5qhXXCB1nSIZOFfqBFQqz+7mtu/ZOvClyCzcrB/NWQCXLMWi725qhiAf435Z6p9OMRIfBVGgL2Mq262EuohjZgQ7wGWU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Dec 24, 2025 at 09:49:38AM +0800, Chen Ridong wrote: > > +nodemask_t cpuset_node_get_allowed(struct cgroup *cgroup) > > { > > Could we define it as: > > void cpuset_node_get_allowed(struct cgroup *cgroup, nodemask_t *node) > > to align with the naming style of node_get_allowed_targets? > > > -bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid) > > +nodemask_t mem_cgroup_node_get_allowed(struct mem_cgroup *memcg) > > void mem_cgroup_node_get_allowed(struct mem_cgroup *memcg, nodemask_t *node) Thanks for the suggestion. Pass a pointer is better. Also, Gregory mentioned that the stack size may be an issue if systems have many nodes. Do you think it is better to use mem_cgroup_node_filter_allowed() to keep the stack size smaller? > > - demotion_nid = next_demotion_node(nid); > > - if (demotion_nid == NUMA_NO_NODE) > > + node_get_allowed_targets(pgdat, &allowed_mask); > > + if (nodes_empty(allowed_mask)) > > + return false; This is a fast-fail path. When the queried node is the farthest node, allowed_mask will be empty. Thus, I would like to keep this check before mem_cgroup_node_get_allowed(). > > + > > + allowed_mems = mem_cgroup_node_get_allowed(memcg); > > + nodes_and(allowed_mask, allowed_mask, allowed_mems); > > + if (nodes_empty(allowed_mask)) > > return false; > > > node_get_allowed_targets(pgdat, &allowed_mask); > mem_cgroup_node_get_allowed(memcg, allowed_mems); > if (!nodes_intersects(allowed_mask, allowed_mems)) > return false; > > Would it look better? Yes, nodes_intersects() is better than logic-and. Will update in v3. Best, Bing