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Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wOsHL-0000000A9JE-24Bl; Mon, 18 May 2026 07:20:44 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id BBF7B300329; Mon, 18 May 2026 09:20:42 +0200 (CEST) Date: Mon, 18 May 2026 09:20:42 +0200 From: Peter Zijlstra To: Tejun Heo Cc: David Vernet , Andrea Righi , Changwoo Min , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Kumar Kartikeya Dwivedi , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Andrew Morton , David Hildenbrand , Mike Rapoport , Emil Tsalapatis , sched-ext@lists.linux.dev, bpf@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 7/8] sched_ext: Sub-allocator over kernel-claimed BPF arena pages Message-ID: <20260518072042.GP3102624@noisy.programming.kicks-ass.net> References: <20260517211232.1670594-1-tj@kernel.org> <20260517211232.1670594-8-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260517211232.1670594-8-tj@kernel.org> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 73986100009 X-Rspam-User: X-Stat-Signature: f3cdth6qdjiay3578n18rukw789udzci X-HE-Tag: 1779088852-238745 X-HE-Meta: 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 jvZWf72+ PmODkPzmULrKYLNBcDFOjmd4rBUhSLHzqTzGhH4+R4u2knvDxzQ7cdyBJHnmQoOhFlC9CQakqu1DZgTxm/PJ6SLAlLQfOkLF0yWpBSZkTJOTBZGAVc+/AWhbPhmKTGwja6v22l77utWzzPvN3+egjZLx1irLa/Xz08iXI4WptDuvNxW2lERDLHlJQdwqIo+5JD+R98s/65kL0zWXpRVw9bKVaH5gAdleq6TPRFUuOJK6z+ISdfQlvGvD+kD96bjn0ydP7IKs80SXM5TM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, May 17, 2026 at 11:12:31AM -1000, Tejun Heo wrote: > Build a per-scheduler sub-allocator on top of pages claimed from the BPF > arena registered in the previous patch. Subsequent kernel-managed > arena-resident structures (e.g. per-CPU set_cmask cmask) carve their storage > from this pool. > > scx_arena_pool_init() creates a gen_pool. scx_arena_alloc() returns the > kernel VA. On exhaustion, the pool grows by claiming more pages via > bpf_arena_alloc_pages_sleepable(). Chunks are added at the kernel-side > mapping address; callers translate to the BPF-arena form themselves if > needed. > > Allocations sleep (GFP_KERNEL) - they may grow the pool through vzalloc and > arena page allocation. All current consumers run from the enable path (after > ops.init() and the kernel-side arena auto-discovery, before validate_ops()), > where sleeping is fine. > > scx_arena_pool_destroy() walks each chunk, returns outstanding ranges to the > gen_pool with gen_pool_free() and then calls gen_pool_destroy(). The > underlying arena pages are released when the arena map itself is torn down, > so the pool destroy doesn't free them explicitly. Should this really be part of scx rather than be part of the bpf-arena thing proper?