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[109.81.32.161]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48de0aaabc3sm3951815f8f.16.2026.10.13.01.22.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Oct 2026 01:22:34 -0700 (PDT) Date: Tue, 13 Oct 2026 10:22:33 +0200 From: Michal Hocko To: Rohit Ner Cc: Johannes Weiner , Roman Gushchin , Shakeel Butt , Andrew Morton , Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/memcontrol: log userspace OOM wait entry and completion Message-ID: References: <20261013040034.3919469-1-rohitner@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261013040034.3919469-1-rohitner@google.com> X-Rspamd-Queue-Id: 6AC77100005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: hf3rdcg7uazg4f4w3jr6kja8psbci465 X-HE-Tag: 1791879756-197475 X-HE-Meta: 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 FH4S79Mq 2RB0mdTyVzK5lQMCbs6nh+FO3+elba9Yhejuukr0csYUL0RlR8qRnA/4aSEmUu2GucoVO6eEmXbE177QRIJzDJp9PNaCdUutfp2Ew3MG+guaWxTBU5YmYHOeosPRsPGC+kLLQwbeigUndyIiOV3zolzjT3abTyTO0+UXzSSlxqP8UzbYTtt0VFC1Y0PO1HOsWcfyffH68S2DScBlP5LEV8zpRfkdCS6cu04j+CrOIKiu/fLTk6JAOITR26wFJXtwcOetWgWneiaOVBf6Uppm5Q5ASiyBuJiEL1brLlCLtT1+C6Ohb6hu7JfPhw3ZJEodzpnRplrto7I0VCp/Yc3YMHwSjrM3hoFlvc+PS Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 13-10-26 04:00:34, Rohit Ner wrote: > When a memory cgroup hits its limit with memory.oom_control > oom_kill_disable configured, mem_cgroup_oom_synchronize() puts the > faulting task to sleep on memcg_oom_waitq and notifies userspace OOM > handlers to reclaim memory, enlarge limits, or terminate tasks. On > platforms where userspace is severely stalled under memory pressure > before a hardware or software watchdog reset, no kernel breadcrumb is > currently emitted when a memcg enters or exits this userspace OOM wait. Correct, this is an inherent limitation of the feature. You rely that the userspace OOM killer implementation is correct and memory pressure aware. > Log rate-limited KERN_ERR messages (pr_err_ratelimited) upon entering > and completing the userspace OOM wait in mem_cgroup_oom_synchronize(), > including the memcg path, memory usage/limit/unevictable stats, elapsed > waited_ms, and whether the task exited due to a fatal signal. Isn't this something you can achieve by adding dynamic tracepoints, bpf progs etc.? Why do we need that for all users? -- Michal Hocko SUSE Labs