From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pdx-out-011.esa.us-west-2.outbound.mail-perimeter.amazon.com (pdx-out-011.esa.us-west-2.outbound.mail-perimeter.amazon.com [52.35.192.45]) (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 D3E5F34041B for ; Thu, 28 May 2026 06:54:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.35.192.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779951288; cv=none; b=VSWKqCItffMaDtBBGg39pWUaYyE9Tlyc4bs6hnw6Odisf2XjOnqQIK1cTrCMn0QzY9sdpC8iclfxEjLEkRe4rmPmBkMxYYu0QDYHU9LAUB57ZkUPEHeIZC/a8zukgRYIYPGor6WQV6pGnEJKwUBvK9x2qHHEJ9LDTqPb1iuxlmc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779951288; c=relaxed/simple; bh=Oc4qlXwQK/HMUjJcQbZI8swYcEJrvQM1Qp+h5zc4yE8=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=j8RBGUGNe7hcRk7iKCRwbH8hb/D3050RIy+fRgpd+Dj+hPKFdC1bKsrjr5yr0bp55ldjxjFXnUwVuX29tLxjJQpwVN9GVMm4VIxu90AyZOqWPSVUbL0JEUPnDUydAG2LGgXxGuC0t5cxdcJXypMMTTQj+nMQiJtTx5ob1D9rXxU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=Jl0uEc/Y; arc=none smtp.client-ip=52.35.192.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="Jl0uEc/Y" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1779951287; x=1811487287; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Oc4qlXwQK/HMUjJcQbZI8swYcEJrvQM1Qp+h5zc4yE8=; b=Jl0uEc/Yzjj+vH8JNzQSFMH2yjUIr+v6JaoeZKZkc8Eal/Zo5PIfrUy4 FJlCQPrjuvbdT+jnJz1yxhecssyLMKap/LaA4i/31sxsF7vp/WlDo9zxG 7rx4v3qEhicucJwttPKFd1a+ignpCMpRefWIj473LAVZYFmGe9u6b4a8i j6zrv4tpFTKbvYa0J5bjC1SOjxXeyK/zGnofxlkdeF+xed0UPE6NHp6rm Y+g7lJkuSJpxQkq8jl0Zh1XzzV3zJ27Cv4l21vn2+7DD3jetymy2rEbjF Q1D89S7Ua1YHU1NxegzUZFs2deJayZOdJr/fbO2eVjQ8SN+3gC/oaG7HD g==; X-CSE-ConnectionGUID: RS8k2q1xRMCTEEH/UUMmgw== X-CSE-MsgGUID: 95s4j5GcQ0qU+3GJLyMYQQ== X-IronPort-AV: E=Sophos;i="6.24,173,1774310400"; d="scan'208";a="20393388" Received: from ip-10-5-0-115.us-west-2.compute.internal (HELO smtpout.naws.us-west-2.prod.farcaster.email.amazon.dev) ([10.5.0.115]) by internal-pdx-out-011.esa.us-west-2.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 May 2026 06:54:43 +0000 Received: from EX19MTAUWC001.ant.amazon.com [205.251.233.53:29455] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.19.88:2525] with esmtp (Farcaster) id 79efb592-8dfc-42b5-aeda-4d7387d753c4; Thu, 28 May 2026 06:54:43 +0000 (UTC) X-Farcaster-Flow-ID: 79efb592-8dfc-42b5-aeda-4d7387d753c4 Received: from EX19D001UWA001.ant.amazon.com (10.13.138.214) by EX19MTAUWC001.ant.amazon.com (10.250.64.174) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.37; Thu, 28 May 2026 06:54:42 +0000 Received: from dev-dsk-sieberf-metal-1a-7543e84d.eu-west-1.amazon.com (172.19.116.227) by EX19D001UWA001.ant.amazon.com (10.13.138.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.37; Thu, 28 May 2026 06:54:39 +0000 From: Fernand Sieber To: CC: , , , , , , , , , , , , , , , Subject: Re: [PATCH 1/2] sched/fair: expose cpu.max.runtime to set bandwidth runtime directly Date: Thu, 28 May 2026 08:54:28 +0200 Message-ID: <20260528065428.69225-1-sieberf@amazon.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: EX19D046UWB004.ant.amazon.com (10.13.139.164) To EX19D001UWA001.ant.amazon.com (10.13.138.214) Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi Tejun, On Wed, May 27, 2026 at 09:04:37AM -1000, Tejun Heo wrote: > On Mon, May 25, 2026 at 09:36:21PM +0200, Fernand Sieber wrote: > > Add a cpu.max.runtime cgroup v2 interface that allows userspace to > > set the CFS bandwidth controller's runtime directly. This enables > > CPU credit injection: an orchestrator writes a runtime budget which > > the cgroup consumes naturally through the existing bandwidth > > enforcement mechanism. > > Can you detail the use case? What problem is it solving how? Our use case is managing CPU credits for VMs. Product spec defines credits accumulation rate (quota), credits limit (burst), and initial level of credits at launch (runtime). Controlling runtime is also necessary for preserving credits across live update (kexec) and live migration. It is possible to approximate this behavior with existing kernel primitives. However this requires setting up awkward parallel accounting/control logic from userspace which must be periodically synced up with the kernel. Instead, we propose minimal changes to the cpu bw primitives to facilitate this use case. Thanks. Fernand Amazon Development Centre (South Africa) (Proprietary) Limited 29 Gogosoa Street, Observatory, Cape Town, Western Cape, 7925, South Africa Registration Number: 2004 / 034463 / 07