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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761674980; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XpykUOb069QPLVeJZBbZFKflqnV60wvcTzlUbFCN+mA=; b=Ub1SN/SJ7bZTNkNA7Mkvwc3LqkUUsEhfF8JeXFibIJIaiIBhX9asAWfHtE1uuPJ2oPqr7Q Yu7c/Wy6sipgogjiJN5d6YT4oOnNFHX8T90X3ykir9AQyVjr/adaQh270IdhWWXzIgVaS1 OhTFaT2XmNcW8sMgw2wYNnQNfgVGO+g= From: Roman Gushchin To: Tejun Heo Cc: Andrew Morton , linux-kernel@vger.kernel.org, Alexei Starovoitov , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Johannes Weiner , Andrii Nakryiko , JP Kobryn , linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Kumar Kartikeya Dwivedi Subject: Re: [PATCH v2 15/23] mm: introduce bpf_task_is_oom_victim() kfunc In-Reply-To: (Tejun Heo's message of "Tue, 28 Oct 2025 07:32:54 -1000") References: <20251027232206.473085-1-roman.gushchin@linux.dev> <20251027232206.473085-5-roman.gushchin@linux.dev> Date: Tue, 28 Oct 2025 11:09:28 -0700 Message-ID: <877bwevqxz.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 41EBC100012 X-Stat-Signature: 3gk7fshixsbpno795gnueicomyhj5j8q X-Rspam-User: X-HE-Tag: 1761674981-747191 X-HE-Meta: U2FsdGVkX1/n/8YXsl/rpk9NHV0FEAfvzFKlh8gwcKrz9D89fmYmVa3OcqtPRBrh9P4VVCeRFjUSUcqbPv+ymJmNhCzO3kG9lyIv/Z81s/tacrNNdWemBpG/GYfunN97ezUA9U21emfnkLOHBJRo+4xviUY0jfrcM2W7nESvhabGi7bjE3gXPaKhw7/1FEgrtj3ovynbwk81C4at2TmMqfWlFZS2HCLzP4EruZ/vK3a6/CB7lKNERn7X/tDmJUX305af82DAWSsXrWLOBFsRLb/5EP7ieZDPCvdkdeN/mfReeqXo3a2ZVkEnY4fD7TCGAA/Q0Wd4nwQgpbAYcVChBOPH/129wsdgjFNXI/u5SsoQu7BoQAwVUTbkBGikYvoRdBPU283RkQGVBKBdf0BhL/EuME3M1AX5PX0Ug+UrlMfyN54fM5xF6pUb+TGEvajroqYitdQfsqeIkd3wo7WMaktGuSOGy/kIyfJyI1VEEwrZ6lvYCu54a8O9NhUqFM9LQdNiY3ETaRxStpvi2Tm8hXecAE4SGIKujYNEY5aHNpNIenYS2AkZyIvAHSQ0PasjQSvsDRf7xnJBMwKLQRbirymMohJhAz7YXnOjoxKvWpne4MtWZimjY9BMfEL96yBXZAOL/alA/lv+RKOaVyGC4z5PDE7zRDhEz8RypzpxkgP7IbQKMnqiJ4rxiNQwpE3/RVJEkM+wdXhQpY2fDH+TJlxr+gL8KXo3a4wZhxMIB9i5IVx49Yq3ERnHXxOXrgJiZMBdPVLTat3sxOWXj5JIeJoUXiIuofMih8iLTRzVYYMEzZQ/ZBsqdmEXEF2m8wuCDeAvIx+oiAZIWFWj2Ts/88VfqEoFLroaihI0VvEnc2wGogqdHZkbq9RoBYsyaoQ7ARjW2hDCAwilLqYK2gPxOQ5TEgEUiuNS 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: Tejun Heo writes: > On Mon, Oct 27, 2025 at 04:21:58PM -0700, Roman Gushchin wrote: >> Export tsk_is_oom_victim() helper as a BPF kfunc. >> It's very useful to avoid redundant oom kills. >> >> Signed-off-by: Roman Gushchin >> --- >> mm/oom_kill.c | 14 ++++++++++++++ >> 1 file changed, 14 insertions(+) >> >> diff --git a/mm/oom_kill.c b/mm/oom_kill.c >> index 72a346261c79..90bb86dee3cf 100644 >> --- a/mm/oom_kill.c >> +++ b/mm/oom_kill.c >> @@ -1397,11 +1397,25 @@ __bpf_kfunc int bpf_out_of_memory(struct mem_cgroup *memcg__nullable, >> return ret; >> } >> >> +/** >> + * bpf_task_is_oom_victim - Check if the task has been marked as an OOM victim >> + * @task: task to check >> + * >> + * Returns true if the task has been previously selected by the OOM killer >> + * to be killed. It's expected that the task will be destroyed soon and some >> + * memory will be freed, so maybe no additional actions required. >> + */ >> +__bpf_kfunc bool bpf_task_is_oom_victim(struct task_struct *task) >> +{ >> + return tsk_is_oom_victim(task); >> +} > > In general, I'm not sure it's a good idea to add kfuncs for things which are > trivially accessible. Why can't things like this be provided as BPF > helpers? I agree that this one might be too trivial, but I added it based on the request from Michal Hocko. But with other helpers (e.g. for accessing memcg stats) the idea is to provide a relatively stable interface for bpf programs, which is not dependent on the implementation details. This will simplify the maintenance of bpf programs across multiple kernel versions. Thanks!