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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c573da455dsm114957785a.115.2025.03.13.09.23.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Mar 2025 09:23:21 -0700 (PDT) Date: Thu, 13 Mar 2025 12:23:19 -0400 From: Gregory Price To: Rakie Kim Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, joshua.hahnjy@gmail.com, dan.j.williams@intel.com, ying.huang@linux.alibaba.com, kernel_team@skhynix.com, honggyu.kim@sk.com, yunjeong.mun@sk.com, david@redhat.com Subject: Re: [PATCH v2 2/4] mm/mempolicy: Support memory hotplug in weighted interleave Message-ID: References: <20250313063351.692-1-rakie.kim@sk.com> Precedence: bulk X-Mailing-List: linux-cxl@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: <20250313063351.692-1-rakie.kim@sk.com> On Thu, Mar 13, 2025 at 03:33:37PM +0900, Rakie Kim wrote: > > I'm fairly certain this logic is wrong. If I add two memory blocks and > > then remove one, would this logic not remove the sysfs entries despite > > there being a block remaining? > > Regarding the assumption about node configuration: > Are you assuming that a node has two memory blocks and that > MEM_OFFLINE is triggered when one of them is offlined? If so, then > you are correct that this logic would need modification. > > I performed a simple test by offlining a single memory block: > # echo 0 > /sys/devices/system/node/node2/memory100/online > > In this case, MEM_OFFLINE was not triggered. However, I need to > conduct further analysis to confirm this behavior under different > conditions. I will review this in more detail and share my > findings, including the test methodology and results. > +David - might have a quick answer to this. I would have expected a single memory block going offline to cause a notification. I think the logic we care about is here: static void node_states_check_changes_online(unsigned long nr_pages, struct zone *zone, struct memory_notify *arg) { int nid = zone_to_nid(zone); arg->status_change_nid = NUMA_NO_NODE; arg->status_change_nid_normal = NUMA_NO_NODE; if (!node_state(nid, N_MEMORY)) arg->status_change_nid = nid; if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY)) arg->status_change_nid_normal = nid; } static void node_states_set_node(int node, struct memory_notify *arg) { if (arg->status_change_nid_normal >= 0) node_set_state(node, N_NORMAL_MEMORY); if (arg->status_change_nid >= 0) node_set_state(node, N_MEMORY); } int online_pages(unsigned long pfn, unsigned long nr_pages, struct zone *zone, struct memory_group *group) { ... node_states_check_changes_online(nr_pages, zone, &arg); ... node_states_set_node(nid, &arg); ... memory_notify(MEM_ONLINE, &arg); } In the callback i think you want to check whether N_MEMORY is set + case MEM_OFFLINE: ++ if (node is !N_MEMORY) ++ sysfs_wi_node_release(node_attrs[nid], wi_kobj); + break; + } Similar with online (don't want to double-add). also from what I can tell, N_MEMORY implies N_ONLINE because N_ONLINE occurs when memory blocks are added (regardless of state). ~Gregory