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From: "JP Kobryn (Meta)" In-Reply-To: <87seabu8np.fsf@DESKTOP-5N7EMDA> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C1A64A0007 X-Stat-Signature: r1kdm6a77neh84ij7d9u18871kr63mz1 X-Rspam-User: X-HE-Tag: 1773030699-309101 X-HE-Meta: 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 KxiyvH4L 3j70eixsGduQGgrBLkwHCCG9V2zqwHW32OSkqzFraTWoLOXHF8LrqxHgHOhgnY6T3QscAWJUKMKXz57HdApktQK2F7BgJY5q4nGbAgsRVHpbcxBUWsQgBkl3BaBnPOMfSONmAPEjNf5oNAhIW8TJNyBHIoVv8kEb1njknoM1apDINOdz3Zoki4CG5Jziu7f8Vu2ONr2QPfr0thEchTYCiX17uMUslZJW9jZLVZH53C/x8zwmtLOg/LqutlsOGUSg8UtAPgvhDl8RgxvvsQ5JckSN32O0Ud9USNoQltXfwXo/6rmLXkkIBnVnoRo4Jw44sHfSgwj5M+LVpHwE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/7/26 4:27 AM, Huang, Ying wrote: > "JP Kobryn (Meta)" writes: > >> When investigating pressure on a NUMA node, there is no straightforward way >> to determine which policies are driving allocations to it. >> >> Add per-policy page allocation counters as new node stat items. These >> counters track allocations to nodes and also whether the allocations were >> intentional or fallbacks. >> >> The new stats follow the existing numa hit/miss/foreign style and have the >> following meanings: >> >> hit >> - for BIND and PREFERRED_MANY, allocation succeeded on node in nodemask >> - for other policies, allocation succeeded on intended node >> - counted on the node of the allocation >> miss >> - allocation intended for other node, but happened on this one >> - counted on other node >> foreign >> - allocation intended on this node, but happened on other node >> - counted on this node >> >> Counters are exposed per-memcg, per-node in memory.numa_stat and globally >> in /proc/vmstat. > > IMHO, it may be better to describe your workflow as an example to use > the newly added statistics. That can describe why we need them. For > example, what you have described in > > https://lore.kernel.org/linux-mm/9ae80317-f005-474c-9da1-95462138f3c6@gmail.com/ > >> 1) Pressure/OOMs reported while system-wide memory is free. >> 2) Check per-node pgscan/pgsteal stats (provided by patch 2) to narrow >> down node(s) under pressure. They become available in >> /sys/devices/system/node/nodeN/vmstat. >> 3) Check per-policy allocation counters (this patch) on that node to >> find what policy was driving it. Same readout at nodeN/vmstat. >> 4) Now use /proc/*/numa_maps to identify tasks using the policy. > Good call. I'll add a workflow adapted for the current approach in the next revision. I included it in another response in this thread, but I'll repeat here because it will make it easier to answer your question below. 1) Pressure/OOMs reported while system-wide memory is free. 2) Check /proc/zoneinfo or per-node stats in .../nodeN/vmstat to narrow down node(s) under pressure. 3) Check per-policy hit/miss/foreign counters (added by this patch) on node(s) to see what policy is driving allocations there (intentional vs fallback). 4) Use /proc/*/numa_maps to identify tasks using the policy. > One question. If we have to search /proc/*/numa_maps, why can't we > find all necessary information via /proc/*/numa_maps? For example, > which VMA uses the most pages on the node? Which policy is used in the > VMA? ... > There's a gap in the flow of information if we go straight from a node in question to numa_maps. Without step 3 above, we can't distinguish whether pages landed there intentionally, as a fallback, or were migrated sometime after the allocation. These new counters track the results of allocations at the time they happen, preserving that information regardless of what may happen later on.