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 428EB19CC2E; Wed, 5 Mar 2025 04:13:08 +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=1741147989; cv=none; b=L9iMVIZ08XyIodZ6rQFgjff5Yt/Xq/yMmRSp1mPimGJSjIkqSEKfQ6Naot4UxK/k3K1lhjMpp6yl6Zhsw7t9Srf5CP8esCgYhp2ARo6d7BQh6kax6BEHp5Gt1DQIbi0lUpfdAQnqafU/A9NA0KB0Y6dG++exSIg1kuOvDcXe6sY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741147989; c=relaxed/simple; bh=5UXRL54BFARNyIExd957ZiQGbmJZmiFrgr7K+zCJvRQ=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=OtIa9iSypeod78YR6HGf70Ie83WD7FCouf7mljgBxSYsK3yHr19gUAz1p8qEKtIYXECrL/fB6lZb5Kr43Rh2AKqVU7zCQBmV+twmluNPrgGBE4BoA7QlO94WfJ2+/lfiwVKIb2rRWU0ei8dRahjz7vrZYzC9VVbKDBWrUdwJcpM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=u4Sk5z5T; 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="u4Sk5z5T" Received: by smtp.kernel.org (Postfix) with ESMTPS id 9E1A8C4CEE2; Wed, 5 Mar 2025 04:13:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741147988; bh=5UXRL54BFARNyIExd957ZiQGbmJZmiFrgr7K+zCJvRQ=; h=From:Subject:Date:To:Cc:Reply-To:From; b=u4Sk5z5Tvo1rTX66Bt3jX/gM1l67V+G3tTXqeLGZnxK671s2GpNj+HMQemd/vrZm0 wDJHZpf2Rx8KRo1JgFqxKDASo8k9mt0iKojjcjUlxXwPswLLIYgK+h0mcJroeJAHEi ljlTgXr2ocZ3Ppjoqf+TuMKIXvGmAddUNXGPA2SReOuuGl6LlsPTUOlovkyjXVJf/O xfzzH5RflCBh7opDD+FEivawhCCvO89WLyOqgKTExCdQLEJA+MU6f8z+o9lWBE9JDX Bk99diqSeVRS6eAax8iUFGYFqS8rNrbw7hN0fwQsSENsRskVSLLVJ9Vcjcsjbm0Tdx /XCZQl5R/1PwA== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F7CEC19F32; Wed, 5 Mar 2025 04:13:08 +0000 (UTC) From: Shashank Balaji via B4 Relay Subject: [PATCH 0/2] cgroup, docs: Clarify interaction of RT processes with cgroup v2 cpu controller Date: Wed, 05 Mar 2025 13:12:42 +0900 Message-Id: <20250305-rt-and-cpu-controller-doc-v1-0-7b6a6f5ff43d@sony.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIADrPx2cC/x3MQQqDQAxA0atI1gZsilZ6leIiZKINyIxkrBRk7 u7g8i3+PyGrm2Z4Nye4HpYtxYpH24B8OS6KFqqBOuo7ogF9R44BZfuhpLh7Wld1DElw5JFZ+hf NT4Xab66z/e/3ZyrlAtNmlBlrAAAA X-Change-ID: 20250226-rt-and-cpu-controller-doc-8a8aac572f3e To: Tejun Heo , Johannes Weiner , =?utf-8?q?Michal_Koutn=C3=BD?= , Jonathan Corbet Cc: Waiman Long , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Shinya Takumi , Shashank Balaji X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1499; i=shashank.mahadasyam@sony.com; h=from:subject:message-id; bh=5UXRL54BFARNyIExd957ZiQGbmJZmiFrgr7K+zCJvRQ=; b=owGbwMvMwCV2mPH4Ij++H1mMp9WSGNKPnw+6+bcjp3D9rkCn1feVrZ4o9OzxMqu4f6zss+Mfs 19xBz23dJSyMIhxMciKKbK8k1l34aCVZdPX4wzfYOawMoEMYeDiFICJzPnJ8IeT757aNhEu/W8p zaGFfgpXFft4k6PfWN7cXqTxv/3Qt2eMDDcUKxsPXbumLzLHV/aM8Jqgpm2y28y37Tm3LGLq95W 6nfwA X-Developer-Key: i=shashank.mahadasyam@sony.com; a=openpgp; fpr=EE1CAED0C13A3982F5C700F6C301C7A24E0EF86A X-Endpoint-Received: by B4 Relay for shashank.mahadasyam@sony.com/default with auth_id=354 X-Original-From: Shashank Balaji Reply-To: shashank.mahadasyam@sony.com Currently, CONFIG_RT_GROUP_SCHED is practically unusable. If enabled, the cpu controller can be enabled only when all the realtime processes are in the root cgroup. This has been clarified by Waiman Long in commit 20d4628 (cgroup, docs: Clarify limitation of RT processes with cgroup v2 cpu controller): https://lore.kernel.org/lkml/20240320142302.1790171-1-longman@redhat.com/ But this limitation does not affect any of the other controllers: irrespective of CONFIG_RT_GROUP_SCHED, the other controllers can be used for the resource control of realtime processes. This is made more explicit in the first patch. Even when CONFIG_RT_GROUP_SCHED is disabled, the runtime of realtime processes is accounted for by cpu.pressure, and the usage_usec, user_usec, and system_usec fields of cpu.stat, and cpu.uclamp.{min, max} affect realtime processes as well. This is documented in the second patch. Signed-off-by: Shashank Balaji --- Shashank Balaji (2): cgroup, docs: Be explicit about independence of RT_GROUP_SCHED and non-cpu controllers cgroup, docs: Document interaction of RT processes with cpu controller Documentation/admin-guide/cgroup-v2.rst | 41 ++++++++++++++++++++++----------- 1 file changed, 27 insertions(+), 14 deletions(-) --- base-commit: 9b381a28f44a49b92b03bb3982728f9cb67ee225 change-id: 20250226-rt-and-cpu-controller-doc-8a8aac572f3e Best regards, -- Shashank Balaji