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 C7BE735C18C; Tue, 21 Apr 2026 07:19:46 +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=1776755986; cv=none; b=t25aI5IeyxTbvQKSdjZS0HTIDZ4kCl9mEcQqNaHUqt3/sd3Z4FLzMhwhjliPECQotRH6xYbHX+9nIt9Z0/sr5f3fw2GZhUPeP/FzfH0q5XQ1djc9k9fUDkmOx9HZfCCoO4TIdLH+rfPASrhjNBYRe0V0DrX2kSTpi52CeKvb/pc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776755986; c=relaxed/simple; bh=hryybqpBE3zbpxQvAS3GplyfvXoVlL2eFAbq0QLsUNA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=okorHXe3JX7IEZLO/77wiK6235icaNSjzUKJMx5n8yxvMdiz6l5Yh5w6cTuQ8w9F4a4i9CqdGBEJo+lt6q/fqWlrFArSkMnFCor9vh2+60SFQ7nKWxEBK6envlTBb8H/FQvSpXxaAxQCH7kWKqH1HGyYrd+JhNXr2waTr71SIwg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BujBubw5; 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="BujBubw5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DDBFC2BCB0; Tue, 21 Apr 2026 07:19:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776755986; bh=hryybqpBE3zbpxQvAS3GplyfvXoVlL2eFAbq0QLsUNA=; h=From:To:Cc:Subject:Date:From; b=BujBubw5hL0tiIZtOeH1yDtyR8lHeRAB+VsRcH1PK0wTJrwyTKAeVquWxpYA1c2f/ VGQsJtR7vHhsb/Io7MdAwagpGBXGgKzxELrfuIbQg/jNM/cyiL7QHqap7Rk5VepB4M 6u+OLp5Kp4Khv0+fIiMtMibQzsTIpPvvr/i35qh7XG0plTJq7ngh0QzfZd6efoer1K 7h4L/in3VHWDsp8UyNWvRlFYJYiytNBK4FRfdleFmLrwxaYsiOZyv27IYSE0R/fm6Q WjKmvowTY86nVzcQmz+xxiOiFSqlQThmF8Dx6mPiG/oZK/0ut22wq9rKNhLCj01q8O MXX94O4UInxsg== From: Tejun Heo To: void@manifault.com, arighi@nvidia.com, changwoo@igalia.com Cc: sched-ext@lists.linux.dev, emil@etsalapatis.com, linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCHSET sched_ext/for-7.2] sched_ext: Topological CPU IDs and cid-form struct_ops Date: Mon, 20 Apr 2026 21:19:29 -1000 Message-ID: <20260421071945.3110084-1-tj@kernel.org> X-Mailer: git-send-email 2.53.0 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, 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. End-to-end testing on a 16-cpu QEMU (identity mapping) and an AMD Ryzen 9 3900X (non-identity cid mapping across CCXes) validated: - cid <-> cpu table roundtrip - SCX_DSQ_LOCAL_ON | cid routing (pinned workers land on the right cpu) - scx_bpf_kick_cid translation (traced entry vs scx_kick_cpu exit) - set_cmask fidelity (bits match cpu_to_cid(task->cpus_ptr)) - idle picker engagement under light load, backoff under saturation - sub-sched qmap (root + 3 subs across cgroups) - cpu-form regression (scx_simple, scx_flatcg still load and schedule) - kfunc filter denial (cid-form calling scx_bpf_task_cpu rejected at load) The patchset depends on a pre-existing bug fix that is being submitted separately to for-7.1-fixes: "tools/sched_ext: scx_qmap: Silence task_ctx lookup miss" https://lore.kernel.org/r/59bc5171ee5aa02746c2f576d0f1e14f@kernel.org The scx-cid-base branch listed below already carries that fix merged through for-7.1-fixes; when for-7.1-fixes is merged back into for-7.2 the dependency resolves naturally. Based on sched_ext/for-7.2 (12ff49d4e1d9) + for-7.1-fixes + the above fix (scx-cid-base at 5755954f68ad). 0001-sched_ext-Rename-ops_cpu_valid-to-scx_cpu_valid-and-.patch 0002-sched_ext-Move-scx_exit-scx_error-and-friends-to-ext.patch 0003-sched_ext-Shift-scx_kick_cpu-validity-check-to-scx_b.patch 0004-sched_ext-Relocate-cpu_acquire-cpu_release-to-end-of.patch 0005-sched_ext-Make-scx_enable-take-scx_enable_cmd.patch 0006-sched_ext-Add-topological-CPU-IDs-cids.patch 0007-sched_ext-Add-scx_bpf_cid_override-kfunc.patch 0008-tools-sched_ext-Add-struct_size-helpers-to-common.bp.patch 0009-sched_ext-Add-cmask-a-base-windowed-bitmap-over-cid-.patch 0010-sched_ext-Add-cid-form-kfunc-wrappers-alongside-cpu-.patch 0011-sched_ext-Add-bpf_sched_ext_ops_cid-struct_ops-type.patch 0012-sched_ext-Forbid-cpu-form-kfuncs-from-cid-form-sched.patch 0013-tools-sched_ext-scx_qmap-Restart-on-hotplug-instead-.patch 0014-tools-sched_ext-scx_qmap-Add-cmask-based-idle-tracki.patch 0015-tools-sched_ext-scx_qmap-Port-to-cid-form-struct_ops.patch 0016-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 kernel/sched/build_policy.c | 1 + kernel/sched/ext.c | 635 +++++++++++++++++++++++++---- kernel/sched/ext_cid.c | 554 +++++++++++++++++++++++++++ kernel/sched/ext_cid.h | 327 ++++++++++++++++ kernel/sched/ext_idle.c | 8 +- kernel/sched/ext_internal.h | 173 +++++++-- tools/sched_ext/include/scx/cid.bpf.h | 595 +++++++++++++++++++++++++++++ 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 | 304 ++++++------- tools/sched_ext/scx_qmap.c | 25 +- tools/sched_ext/scx_qmap.h | 2 +- 12 files changed, 2419 insertions(+), 252 deletions(-) -- tejun