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b=O3p0WQEIUGSnM4o9AHaajsmMzyXtje/e+dTwxse4bN5LQdDVpnlXIeYjt/qk6Lhuk ziW02G6yvHytQux0Qfk06MJ8uEI1YmngtL9f5qbw+uGzMEwRAv6xhBlZ4TUBm8EGFY qkkMNMviYPPgQJ3GYrkYaUwaNZKRlWm+eDt4NsnynJ3GAFqnpN8JSrKTuBx6CmwmeK vrMmJAURMYrBZM0Vbfg9m/bIiw0cvsjkeUHXKKSddgpAq7xT4zID50tyImZj9oEsVj ZfoghU3I4SIRxfJ0YXqk/x2VKBsv9pDA9F0XnpgmNRloxfe5GFJFT+MBpQRXcah/m3 YqcJ/4T8EmBfA== Date: Mon, 11 May 2026 12:25:12 +0100 From: Lorenzo Stoakes To: "David Hildenbrand (Arm)" Cc: Vernon Yang , akpm@linux-foundation.org, roman.gushchin@linux.dev, inwardvessel@gmail.com, shakeel.butt@linux.dev, ast@kernel.org, daniel@iogearbox.net, surenb@google.com, tz2294@columbia.edu, baohua@kernel.org, lance.yang@linux.dev, dev.jain@arm.com, laoar.shao@gmail.com, gutierrez.asier@huawei-partners.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Vernon Yang Subject: Re: [PATCH v2 3/4] mm: introduce bpf_mthp_ops struct ops Message-ID: References: <20260508150055.680136-1-vernon2gm@gmail.com> <20260508150055.680136-4-vernon2gm@gmail.com> <5987cdee-9174-44fb-8e2b-41e6ad969612@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5987cdee-9174-44fb-8e2b-41e6ad969612@kernel.org> X-Stat-Signature: 6yjpmexd9bugj5jfg33yqt5as5nagtz3 X-Rspamd-Queue-Id: C6F84100011 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1778498720-149261 X-HE-Meta: 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 mI2FGeCt IGExhL8FvMDFsA8m6mw+cynwcgGJq/IugMQauGe1zkyRSvkSPsE713KiGpEK/cWtCConqWThHowQzMDd9s8gc1xIheb9ZxA/1N8aRrpGnxj0T68qP1CoKfJm71iuupCW014LlrNxvzsHxZegwxt4x7AENPHuecvn04DEQOKA4rsv3GL+v5E1E37Vpj8qU9xjXgO4UDtG0e/r3avvhpj7ddF+2ZSOujSeP6p2fypWrkF58CLI+z7GRrG+bwCqyLNfcvvbnAuRaBlwt7t/dqc9cgwvvkVRFLVJZzXWFrkrDYpiIXBTsv7lTAOmQAojm8XE9ITJXu3BBwLWT2FH5s3pGKqwThYbmlRjLoxfI0q7PmvKcHj4goH69crWzKcRqLWt2p7uFPT35x5NfCsA1copPBNbw2GhzuvMqFuTz9yW8z4PampI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 08, 2026 at 10:54:58PM +0200, David Hildenbrand (Arm) wrote: > > > > #include /* only for vma_is_dax() */ > > #include > > @@ -296,6 +297,11 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma, > > enum tva_type type, > > unsigned long orders) > > { > > + /* The eBPF-specified orders overrides which order is selected. */ > > + orders &= bpf_mthp_choose(vma->vm_mm, orders); > > + if (!orders) > > + return 0; > > + > > There was some discussion around this in the past: where should we hook into > (e.g., deferred shrinker?), which information should we provide to the hook > (e.g., vma properties?). > > We concluded mostly to "we don't know". I know that Rik van Riel wanted to look > into doing this properly, but seems like he got distracted :) > > I assume there will be a lwn.net article covering the "BPF in MM" session we had > at LSF/MM just this week. > > Conclusion: ABI stability is a headake. > > The simplistic approach of deciding an order for the whole MM is very likely not > what we want. Agreed with all points! > > -- > Cheers, > > David Cheers, Lorenzo