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b=F6PhZS4h4d4Jm70pbTD/Zfvh2zE6PPSle2THnyGlLX/hJnApn3A30pp1+KONryzHU G4vMy07i+dWaiV9Unw3bEjkSfMgDiy7LXqA56qdwBWgka3hIyIVGQSWk2MePRwBx7j by9zJmb6zmYL8BLUqVOcMrzFgDmqwdvyZ1uVttNzM1bmaEqefuWoie+ML0wRMrF2Jp NH/vu3oNwHKj8LWnuB3SzolEAi4kJY1f79MhEFq0AzJWrGWfNysT9A4kxC/XDJa1LL aZiOGqNN/KPM4BvnP8NrgOWRpUngIuHXzBzvQvMMTuCV6W7F+r9DhOSQfDBE3vgeK3 BYINY2jsETllQ== Date: Wed, 29 Oct 2025 11:45:46 -1000 From: Tejun Heo To: Song Liu Cc: Roman Gushchin , 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 , Kumar Kartikeya Dwivedi Subject: Re: [PATCH v2 02/23] bpf: initial support for attaching struct ops to cgroups Message-ID: References: <20251027231727.472628-1-roman.gushchin@linux.dev> <20251027231727.472628-3-roman.gushchin@linux.dev> <87ldkte9pr.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: D99352000C X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: 8kicc76yxenpaqwxw4fkdsjx6iu7zn18 X-HE-Tag: 1761774348-876078 X-HE-Meta: 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 ZYZC4Euq YUGAK0g34F4Yz57eOiRNxEn49k7zglzutcBpboC9JfDBE+xoohw8+wWTLCh3M7Fam7A7NcWSwrRvM6zaAR/qUKyS44UGn7dLarxEZG+YQ5leheYNOXiZ/MLCIJRJpf90LCoZev9b+3zEVbvUAxhmsP9RICzwq8DbjWiikLF+OTgomJNjhcuw1FXUiFg6UlA8EpH0tWvalrMIMJm1eeWSO3qWvqrVHoK3pVNWUVvGc4CbYLHsQ8oTOLzTme9ZE44zx0eCg 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: Hello, On Wed, Oct 29, 2025 at 02:37:38PM -0700, Song Liu wrote: > On Wed, Oct 29, 2025 at 2:27 PM Tejun Heo wrote: > > Doesn't that assume that the programs are more or less stateless? Wouldn't > > oom handlers want to track historical information, running averages, which > > process expanded the most and so on? > > Yes, this does mean the program needs to store data in some BPF maps. > Do we have concern with the performance of BPF maps? It's just a lot more awkward to do and I have a difficult time thinking up reasons why one would need to do that. If you attach a single struct_ops instance to one cgroup, you can use global variables, maps, arena to track what's happening with the cgroup. If you share the same struct_ops across multiple cgroups, each operation has to scope per-cgroup states. I can see how that probably makes sense for sockets but cgroups aren't sockets. There are a lot fewer cgroups and they are organized in a tree. Thanks. -- tejun