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[109.81.31.109]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-64179499189sm3896343a12.8.2025.11.10.01.46.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Nov 2025 01:46:16 -0800 (PST) Date: Mon, 10 Nov 2025 10:46:15 +0100 From: Michal Hocko To: Roman Gushchin Cc: Andrew Morton , linux-kernel@vger.kernel.org, Alexei Starovoitov , Suren Baghdasaryan , 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 , Tejun Heo Subject: Re: [PATCH v2 13/23] mm: introduce bpf_out_of_memory() BPF kfunc Message-ID: References: <20251027232206.473085-1-roman.gushchin@linux.dev> <20251027232206.473085-3-roman.gushchin@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@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: <20251027232206.473085-3-roman.gushchin@linux.dev> On Mon 27-10-25 16:21:56, Roman Gushchin wrote: > Introduce bpf_out_of_memory() bpf kfunc, which allows to declare > an out of memory events and trigger the corresponding kernel OOM > handling mechanism. > > It takes a trusted memcg pointer (or NULL for system-wide OOMs) > as an argument, as well as the page order. > > If the BPF_OOM_FLAGS_WAIT_ON_OOM_LOCK flag is not set, only one OOM > can be declared and handled in the system at once, so if the function > is called in parallel to another OOM handling, it bails out with -EBUSY. > This mode is suited for global OOM's: any concurrent OOMs will likely > do the job and release some memory. In a blocking mode (which is > suited for memcg OOMs) the execution will wait on the oom_lock mutex. Rather than relying on BPF_OOM_FLAGS_WAIT_ON_OOM_LOCK would it make sense to take the oom_lock based on the oc->memcg so that this is completely transparent to specific oom bpf handlers? -- Michal Hocko SUSE Labs