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Thu, 04 Sep 2025 07:26:30 -0700 (PDT) From: Joshua Hahn To: Jinjiang Tu Cc: mhocko@suse.com, rientjes@google.com, shakeel.butt@linux.dev, akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, wangkefeng.wang@huawei.com Subject: Re: [PATCH] mm/oom_kill: kill current in OOM when binding to cpu-less nodes Date: Thu, 4 Sep 2025 07:26:25 -0700 Message-ID: <20250904142626.1146459-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250904134431.1637701-1-tujinjiang@huawei.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C0B9D14000E X-Stat-Signature: euz3hda8mk6dnwwmn4n4rdnp68s9tyci X-Rspam-User: X-HE-Tag: 1756995991-989106 X-HE-Meta: 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 RXOtXvgL 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 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 Thu, 4 Sep 2025 21:44:31 +0800 Jinjiang Tu wrote: Hello Jinjiang, I hope you are doing well, thank you for this patchset! > out_of_memory() selects tasks without considering mempolicy. Assuming a > cpu-less NUMA Node, ordinary process that don't set mempolicy don't > allocate memory from this cpu-less Node, unless other NUMA Nodes are below > low watermark. If a task binds to this cpu-less Node and triggers OOM, many > tasks may be killed wrongly that don't occupy memory from this Node. I am wondeirng whether you have seen this happen in practice, or if this is just based on inspecting the code. I have a feeling that the case you are concerned about may already be covered in select_bad_process. out_of_memory(oc) select_bad_process(oc) oom_evaluate_task(p, oc) oom_cpuset_eligible(task, oc) [...snip...] for_each_thread(start, tsk) { if (mask) { ret = mempolicy_in_oom_domain(tsk, mask); } else { ret = cpuset_mems_allowed_intersects(current, tsk) } } While iterating through the list of candidate processes, we check whether oc->nodemask exists, and if not, we check if the nodemasks intersects. It seems like these are the two checks that you add in the helper function. With that said, I might be missing something obvious -- please feel to correct me if I am misunderstanding your patch or if I'm missing something in the existing oom target selection : -) I do see that with your patch, we avoid having to go through select_bad_process and we just go straight to choosing the current task, which I can definitely see as an argument. But in that case I think this patch's description would be more of an optimization, and less of a fix since the behavior is already accounted for. Again, please feel free to correct me : -) I hope you have a great day! Joshua Sent using hkml (https://github.com/sjp38/hackermail)