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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cee6023d6sm225255635e9.8.2026.09.05.04.24.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 05 Sep 2026 04:24:54 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Sat, 05 Sep 2026 13:24:53 +0200 Message-Id: From: "Kumar Kartikeya Dwivedi" To: "Hui Zhu" , "Roman Gushchin" , "JP Kobryn" , "Shakeel Butt" , "Andrew Morton" , "Andrii Nakryiko" , "Eduard Zingerman" , "Ihor Solodrai" , "Alexei Starovoitov" , "Daniel Borkmann" , "Martin KaFai Lau" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "Emil Tsalapatis" , "Shuah Khan" , "Barry Song" , "Geliang Tang" , , , , Cc: "Hui Zhu" Subject: Re: [PATCH bpf-next v7 0/2] bpf: BPF-driven proactive memcg reclaim X-Mailer: aerc 0.21.0 References: In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: F351FA0009 X-Stat-Signature: 8zb3zcxfjf1qtddgg1kjrthec79wi47t X-HE-Tag: 1788607496-61876 X-HE-Meta: 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 05k7AKXM nXN1UZPMv3RNRR1RyJk+FonJ9MPeYR81f9VhpNmquK/poOlmN/M6H6z8/fwr6qC4+L66X9oPXSh3pAzWqjAanI/N+l2aioAXmaHQm2Zf6NiGoJD/aQYp+nJQkHHHRey4NbW7t7jJ4rTVSXRfj16y7xj1itGgirERXEKbGQrv+eDfKr/zOasEfiYGGW0xyaDO9mgQ4amRqFeDSvPsvMRT2v0xx9oaY6vcJ7x+ylHoGq6VfqURfzLhZt8WBd3Ifx+46mrW67dQPRkRTFjGVh4jEV+o0aRIKl1JUY/Bwo786i/9exZNbI+/gmc3G8DkGkwpvDEUvaVyXSo/HERItYvK4Uz9G5orrf6iMooYUZ/pfOQcnlh69WihjQMLZbI8yPbbfvQeJ3Txwq/9kEHLp/a0JOF02zdTwRmgrOofYfGjYL6f5IJBG9vM9MhQusMogC+Ym0LrZSLzIKbb0sNjvU9nVA2uBwn8dKipKoul8 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri Sep 4, 2026 at 12:20 PM CEST, Hui Zhu wrote: > From: Hui Zhu > > BPF programs can observe memory pressure on a cgroup (e.g. refault > stats via bpf_mem_cgroup_page_state()), but cannot act on it: > triggering reclaim on a chosen cgroup requires writing to > memory.reclaim, which BPF cannot do. This series adds > bpf_proactive_reclaim(), a sleepable kfunc performing one proactive > reclaim pass on a target memcg, so when and how hard to reclaim is > BPF policy rather than hard-coded thresholds. > > The kfunc is restricted to BPF_PROG_TYPE_SYSCALL so that reclaim > always runs in a clean process context: generic sleepable programs > may execute with filesystem locks held or in NOFS/NOIO contexts, > where the reclaim path could deadlock in filesystem shrinkers. The > bpf_wq and task_work callbacks of a SYSCALL program keep its program > type and run in process context, so reclaim work can still be queued > asynchronously through them, as the selftest does with bpf_wq. > > The use case we are looking at is protecting high-priority workloads: > a BPF program monitors the state of a high-priority cgroup and, when > it degrades (e.g. PSI rises or refaults increase, as in the > selftest), asynchronously reclaims memory from low-priority cgroups > via bpf_wq and bpf_proactive_reclaim(), giving the pressured cgroup > more free pages. > > Another use case: several vendor-maintained kernels carry private > implementations that trigger asynchronous reclaim when a memcg enters > a certain state. These exist for historical and partly psychological > reasons, but the underlying demand is real. We expect BPF-driven > proactive reclaim, combined with the BPF hooks for the memory > controller currently under discussion and development, to serve these > needs in mainline, reducing kernel fragmentation and improving kernel > maintainability. >From BPF perspective this looks ok to me. I saw you dropped the swappiness argument, what happened there? I thought we agreed to just include it in th= e kfunc now. Did something change?