From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83B222E7623; Tue, 28 Apr 2026 20:35:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777408547; cv=none; b=kidIVGgrd+UEiqApTnYdgadvGtp8vy2Vzx3/Q+SNK0MPupj6wNarIr7h+OfsJ6HsRknVItP2ZS3gt87G6uUDeWlxIIE466AjcioZDUWEnRlo9J3Sw1zubIvYEdUI5STIhhJqt4ikZBBFZiGI+9QFVbfGtmWqA386kgXHVn67Xww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777408547; c=relaxed/simple; bh=SF+gMmHC0/V+w4B5gtgrq96vcjIFcd74d0xu9BHaX/U=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=IhV1wZsJ+r8ZP7GyVKpRSsCoUDJpw5gJ7pxab8QnXfaJMLT1vdKyH1Ie/IrnYjf22hw1zh72y1FDT5SFQnhiSdDju5DIjUmP5Z8/775NDIoHEl9Q8+hqrJewT62BkP8MHBvJLWycil2zJToPUOYgLEr7NfL/Rc0Zv/7+TIYSttc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hssoJTIS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hssoJTIS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D3BDC2BCB3; Tue, 28 Apr 2026 20:35:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777408547; bh=SF+gMmHC0/V+w4B5gtgrq96vcjIFcd74d0xu9BHaX/U=; h=From:To:Cc:Subject:Date:From; b=hssoJTISbcliOI7QJYhcuGs84QL7W8SDOAYGru7UKYPOqAVCOpLLBLLvZ34o0BQQ7 NxITB/bKwA8qGMKe0sAF40kwiMvN2nArHxInIi6+RghPhT7P5++i2lF/FcnIAqKZJ1 EAW0V2Hkiv6JhlcWqfV0f+guIpIW2R8xh7AMIus09Y+2XRAw9GDv8cbozxnTxdm6Os 2gcKNna07Ej19ZdIYqZ0jCGHUmrxbLq5UREFVoCER4CvB5BN8eIYb7aQlZxOX99xAg 6blJoAZ7RdKf6yY2dx/TOwU6XbQxJRI0YHZ+hb0V44rXBi4VTsYR5P+X8T0+XRB+y+ oieODSROkSK1Q== From: Tejun Heo To: David Vernet , Andrea Righi , Changwoo Min Cc: sched-ext@lists.linux.dev, Emil Tsalapatis , linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCHSET v3 sched_ext/for-7.2] sched_ext: Topological CPU IDs and cid-form struct_ops Date: Tue, 28 Apr 2026 10:35:28 -1000 Message-ID: <20260428203545.181052-1-tj@kernel.org> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hello, v3 (all from the Sashiko AI review at https://sashiko.dev/#/patchset/20260424172721.3458520-1-tj%40kernel.org): - cid: drop leaked cpus_read_lock() on scx_cid_init() failure; BUILD_BUG_ON tightened to NR_CPUS<=8192 to match the BPF cmask helpers' CMASK_MAX_WORDS coverage. - bpf-struct-size: use offsetof() in struct_size() to match the kernel macro semantics (no inflation from trailing struct padding). - cmask: cmask_copy_from_kernel() validates src->base==0 via probe-read; nr_bits check is bit-level rather than rounded-up word-count. - cid-qmap-idle: qmap_init() refuses to load when scx_bpf_nr_cids() exceeds SCX_QMAP_MAX_CPUS; the task_ctx flex array would otherwise overflow into the next slab entry. v2: https://lore.kernel.org/r/20260424172721.3458520-1-tj@kernel.org v1: https://lore.kernel.org/r/20260421071945.3110084-1-tj@kernel.org This patchset introduces topological CPU IDs (cids) - dense, topology-ordered cpu identifiers - and an alternative cid-form struct_ops type that lets BPF schedulers operate in cid space directly. Key pieces: - cid space: scx_cid_init() walks nodes * LLCs * cores * threads and packs a dense cid mapping. The mapping can be overridden via scx_bpf_cid_override(). See "Topological CPU IDs" in ext_cid.h for the model. - cmask: a base-windowed bitmap over cid space. Kernel and BPF helpers with identical semantics. Used by scx_qmap for per-task affinity and idle-cid tracking; meant to be the substrate for sub-sched cid allocation. - bpf_sched_ext_ops_cid: a parallel struct_ops type whose callbacks take cids/cmasks instead of cpus/cpumasks. Kernel translates at the boundary via scx_cpu_arg() / scx_cpu_ret(); the two struct types share offsets up through @priv (verified by BUILD_BUG_ON) so the union view in scx_sched works without function-pointer casts. Sub-sched support is tied to cid-form: validate_ops() rejects cpu-form sub-scheds and cpu-form roots that expose sub_attach / sub_detach. - cid-form kfuncs: scx_bpf_kick_cid, scx_bpf_cidperf_{cap,cur,set}, scx_bpf_cid_curr, scx_bpf_task_cid, scx_bpf_this_cid, scx_bpf_nr_{cids,online_cids}, scx_bpf_cid_to_cpu, scx_bpf_cpu_to_cid. A cid-form program may not call cpu-only kfuncs (enforced at verifier load via scx_kfunc_context_filter); the reverse is intentionally permissive to ease migration. - scx_qmap port: scx_qmap is converted to cid-form. It uses the cmask-based idle picker, per-task cid-space cpus_allowed, and cid-form kfuncs throughout. Sub-sched dispatching via scx_bpf_sub_dispatch() continues to work. v3 re-tested on the 16-cpu QEMU: cid-form scx_qmap under stress-ng plus reload cycles, hotplug auto-restart, and sub-sched (root scx_qmap + cgroup-scoped scx_qmap child). Clean. Based on sched_ext/for-7.2 (4939721aad2e). 0001-sched_ext-Add-ext_types.h-for-early-subsystem-wide-d.patch 0002-sched_ext-Rename-ops_cpu_valid-to-scx_cpu_valid-and-.patch 0003-sched_ext-Move-scx_exit-scx_error-and-friends-to-ext.patch 0004-sched_ext-Shift-scx_kick_cpu-validity-check-to-scx_b.patch 0005-sched_ext-Relocate-cpu_acquire-cpu_release-to-end-of.patch 0006-sched_ext-Make-scx_enable-take-scx_enable_cmd.patch 0007-sched_ext-Add-topological-CPU-IDs-cids.patch 0008-sched_ext-Add-scx_bpf_cid_override-kfunc.patch 0009-tools-sched_ext-Add-struct_size-helpers-to-common.bp.patch 0010-sched_ext-Add-cmask-a-base-windowed-bitmap-over-cid-.patch 0011-sched_ext-Add-cid-form-kfunc-wrappers-alongside-cpu-.patch 0012-sched_ext-Add-bpf_sched_ext_ops_cid-struct_ops-type.patch 0013-sched_ext-Forbid-cpu-form-kfuncs-from-cid-form-sched.patch 0014-tools-sched_ext-scx_qmap-Restart-on-hotplug-instead-.patch 0015-tools-sched_ext-scx_qmap-Add-cmask-based-idle-tracki.patch 0016-tools-sched_ext-scx_qmap-Port-to-cid-form-struct_ops.patch 0017-sched_ext-Require-cid-form-struct_ops-for-sub-sched-.patch Git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-cid-v3 kernel/sched/build_policy.c | 3 + kernel/sched/ext.c | 651 ++++++++++++++++++++++++++---- kernel/sched/ext_cid.c | 409 +++++++++++++++++++ kernel/sched/ext_cid.h | 164 ++++++++ kernel/sched/ext_idle.c | 8 +- kernel/sched/ext_internal.h | 205 +++++++--- kernel/sched/ext_types.h | 104 +++++ tools/sched_ext/include/scx/cid.bpf.h | 667 +++++++++++++++++++++++++++++++ tools/sched_ext/include/scx/common.bpf.h | 23 ++ tools/sched_ext/include/scx/compat.bpf.h | 24 ++ tools/sched_ext/scx_qmap.bpf.c | 346 +++++++++------- tools/sched_ext/scx_qmap.c | 70 +++- tools/sched_ext/scx_qmap.h | 2 +- 13 files changed, 2391 insertions(+), 285 deletions(-) Thanks. -- tejun