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Sun, 03 May 2026 10:25:32 -0700 (PDT) Received: from localhost.localdomain ([114.231.84.174]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-83515b1fe12sm8672423b3a.47.2026.05.03.10.25.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 May 2026 10:25:31 -0700 (PDT) Date: Mon, 4 May 2026 01:25:25 +0800 From: Vernon Yang To: "David Hildenbrand (Arm)" Cc: Roman Gushchin , bpf , linux-mm , Vlastimil Babka , Shakeel Butt , Andrew Morton , lsf-pc , Daniel Borkmann Subject: Re: [LSF/MM/BPF TOPIC] Using BPF in MM Message-ID: <821acd4c-d443-44d0-842d-26ff45e2f54d@gmail.com> References: <7ia4o6j4c5y1.fsf@castle.c.googlers.com> <014f3c0a-7c6f-4f64-95cd-b7b69d804880@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <014f3c0a-7c6f-4f64-95cd-b7b69d804880@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 7C340120004 X-Stat-Signature: 9o5xdahkwea7xps3a5qe6b9f4w96nks6 X-HE-Tag: 1777829133-698569 X-HE-Meta: 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 2xTXHOWa 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 28, 2026 at 10:12:16AM +0200, David Hildenbrand (Arm) wrote: > On 4/28/26 01:57, Roman Gushchin wrote: > > [LSF/MM/BPF TOPIC] Using BPF in MM > > ---------------------------------- > > > > Over the last decade, BPF successfully penetrated into multiple kernel > > subsystems: started as a feature to filter (out) networking packets, > > it captured its place in networking, tracing, security, HID drivers, > > and scheduling. Memory management is a logical next step, and recently > > we saw a growing number of proposals in this area. > > > > In (approximately) historical order: > > - BPF OOM > > - BPF-based memcg stats access (landed) > > - BPF-based NUMA balancing > > - eBPF-mm > > - cache_ext (BPF Page Cache) > > - memcg_ext > > There was also the BPF THP control. Hi David, Roman, I submit a new series "mm: introduce mthp_ext via cgroup-bpf to make mTHP more transparent"[1] to implement BPF-THP, which has excellent performance data through stress testing. For details, please refer to the patchset cover letter. Although I did not attend the conference in person, I have been online throughout. Please feel free to discuss any latest progress with me online. Thank you! [1] https://lore.kernel.org/linux-mm/20260503165024.1526680-1-vernon2gm@gmail.com/ -- Cheers, Vernon > > > > There are some obvious target which haven't been covered yet: > > - BPF-driven readahead control > > - BPF-driven KSM > > - BPF-driven guest memory control > > > > Despite a large number of suggestions only a relatively small feature > > (query memcg statistics from BPF) made it to upstream. > > > > It looks like using BPF in the MM subsystem comes with a set of somewhat > > unique challenges and questions to be answered. > > [...] > > I think you are missing one of the most important points: Unclear ABI stability > guarantees. > > One the one hand, we are told that there are no ABI stability guarantees, and > that we can change hooks (add/remove/modify) any time we want. > > On the other hand, as soon as there is some ebpf program out there that we > break, you can rest assured that there will be trouble. > > In the area of THP, where we don't even know which hooks we will need long term > and how they would look like, that was one of the reasons why the BPF THP > control was rejected. > > -- > Cheers, > > David >