From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from AM0PR02CU008.outbound.protection.outlook.com (mail-westeuropeazon11023098.outbound.protection.outlook.com [52.101.72.98]) (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 649372FB092 for ; Fri, 24 Oct 2025 08:02:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.72.98 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761292962; cv=fail; b=ndl4V4T45KvGsKmQuEFQnp9a1raNTfRATuQeoj9kUGpZ+aFcn1/OlOR2XqnZ2HzJhFUvEEXtrZqoY8OR4akD96gqFdVQKMjfecOF4WbuFfxXR9uOglvsRIsfzVhe5q3mtDEfZpIZ1WSQAA+1CuXewHHfAkLmw7C0kFggYBI5F2U= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761292962; c=relaxed/simple; bh=TgtvTE3LQIvdoLMiblvzyNG9gaDynvYSswf58bhaYq8=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=sL5uO5JBt6zUXDx9jlSwLZdKf15UmFZewMvbMrG3MP3vmpo8voeiBTroMmyILmocmuvu1KGVg0GHiinMYp4b/knAZlJ/Hho44oVHzTuzqVDIDznLPo1DrOHKg2F7ktDI/g8OhaUQYideV56kz+f6USTQyBh8ZMKv7g7b7vqTYuA= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=santannapisa.it; spf=pass smtp.mailfrom=santannapisa.it; dkim=pass (1024-bit key) header.d=santannapisa.it header.i=@santannapisa.it header.b=JVSpUZm/; arc=fail smtp.client-ip=52.101.72.98 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=santannapisa.it Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=santannapisa.it Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=santannapisa.it header.i=@santannapisa.it header.b="JVSpUZm/" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=nPtJLyYJYyC1SsXmuT3Vswv8l1WieeaQx2sfG647VaFGfcSSz4BzCwm2tPvsC811cxajQ1nCvW3dpTQWuRQLlNMgLR8hhHmBXK0wUj2OcLuKdpPdhGJP9EDpsvq1lAJNvmvXocQqNAoZmpnar9VFYyEgGcKOlTh0srOHOw/Y85HCgS9AqZGBCLP6uYECO6H79Jmo7IOVADiVhpy8kI4TjD+noHVZt2R2yMhASBcfvTTtk/MFIvI9SjnFYNMQTSVPp05PSAkPd4nICv4lGJW9xqrZ+i/BlHidbHBje2e2DVgg+i4AX3BohTqcb80qGGsbcyZjD1Ypzl9Xa8/zu8iWWQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=hGX23FcA0GHMRJWk4C13az1kY2o6af8sR4vEYxjofvY=; b=IPfgxk3xyBN+PoqqsInWYhYHZ6ZgYuXZuq6nYBUEt87YVODcAk4WNNB3xh/hl2qWMvrQ7df8RYUG9A77ZRcWgwFbBwffiNm4qGe+ZxA8RmqX6XL6xtri/dl/dbb6filYsUmxh4yy8JaXGgeOkbdZI8qpQ3SKnXRHniFMjdzn8cOT+NqOCkeBRJdpzu5ejMznT+gaBlyK07pg1cGH4ADP3L2ynyPtXBhiy4yCMDGMDcbz7MzrLIYp418gNKeYgYOgAG+sq5r1HinX9BB+VvtvRu50sMgmSbLUcSsfEl6lA23MfP4C5VwkDGFZn6vYrsgTmOPfCUoCrS5MxHYvZEzlYw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=santannapisa.it; dmarc=pass action=none header.from=santannapisa.it; dkim=pass header.d=santannapisa.it; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=santannapisa.it; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=hGX23FcA0GHMRJWk4C13az1kY2o6af8sR4vEYxjofvY=; b=JVSpUZm/OkMqjcvB860UMk/TyUBZuZTvt/wBE6+XBwbooBT8eEaQdwqkoz1rqNXmKalg7BA6oIJ9MzFmMVD9qKt+e+RGUpwyfxUJWWss+1unHGzmQO9HGP2YnpaWQ4hHH5WcvNxfeZN1AFKsjJa4L3ouovuhCnA51IbKNQd4Y1I= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=santannapisa.it; Received: from PAVPR03MB8969.eurprd03.prod.outlook.com (2603:10a6:102:32e::7) by AS8PR03MB10149.eurprd03.prod.outlook.com (2603:10a6:20b:630::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9253.12; Fri, 24 Oct 2025 08:02:31 +0000 Received: from PAVPR03MB8969.eurprd03.prod.outlook.com ([fe80::6bbe:2e22:5b77:7235]) by PAVPR03MB8969.eurprd03.prod.outlook.com ([fe80::6bbe:2e22:5b77:7235%4]) with mapi id 15.20.9253.011; Fri, 24 Oct 2025 08:02:31 +0000 Date: Fri, 24 Oct 2025 10:02:27 +0200 From: luca abeni To: Juri Lelli Cc: Yuri Andriaccio , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-kernel@vger.kernel.org, Yuri Andriaccio Subject: Re: [RFC PATCH v3 00/24] Hierarchical Constant Bandwidth Server Message-ID: <20251024100227.6ab1bfde@luca64> In-Reply-To: References: <20250929092221.10947-1-yurand2000@gmail.com> Organization: Scuola Superiore S. Anna X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-pc-linux-gnu) Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-ClientProxiedBy: ZR2P278CA0080.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:65::10) To PAVPR03MB8969.eurprd03.prod.outlook.com (2603:10a6:102:32e::7) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PAVPR03MB8969:EE_|AS8PR03MB10149:EE_ X-MS-Office365-Filtering-Correlation-Id: ac0b1f89-7d3a-4d20-0c2f-08de12d3ae76 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014|7053199007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?TeCyPkT+QSeAMPqDxA3d99RRPsNvX47c43Bj5rMMxi5j2u++CleTn41Vza1E?= =?us-ascii?Q?AHWLyUtVEjTFCpePIrUQBlvCAjfLgnrckoOx4kfmlP2hlvR2TwAHSjrGgJWG?= =?us-ascii?Q?b+NOuvjdgRwm20/Z6j1+8lcemeC8nb3I9eQu7hmb6oZTk+yvVMRGtoG4lhlA?= =?us-ascii?Q?GVPv1b6bI+MaOdJ6cMc3blqEm+wfa0GN5yp42Yg4wA7ZAKXUi1aSPCb6mUzI?= =?us-ascii?Q?mOqG9XC7aXNjGcEVR87I6QGBZ2HrgTrgp9VInrMo/ppI0ZxwkbP34ZMkVor7?= =?us-ascii?Q?Znamxp5nXIVsPdAiXEk8s1yfJYzV2/pLaMuJzOIgOUi3rU92v+MkZ1ofGqab?= =?us-ascii?Q?Vb/Mxm9xJL+8iinF1ICYOqGt2yiMmLQ0p0A4AlMHneA+iz5zI5CTpluOC/g3?= =?us-ascii?Q?TPZRgdWjoX2xYRI+/PYYwYi0spVFHXxzjICjltzOGQNr8G59h9kGv8VfM6GP?= =?us-ascii?Q?a80QqNiRNk8tMIhViDKRYaqsayuIXCxdhK9ufBwzdgJ0dfFE88wXqOlkgKKY?= =?us-ascii?Q?PYdLEBj2rDw0ADvEHeR2rsOS6Z+yj5j3W/Et5XIPlLCpHaC6OfqAJrvWZ+vu?= =?us-ascii?Q?ps7s0AeZpsLTyPkMh/fQ59FACITIjDRCCHyHhqv3dT7frDWlSuDedtFvTOrs?= =?us-ascii?Q?C54ALpk5I8HbM/6aKOnwutVz4Bj+jr3whByLNJAJIq3JKb4+Io0Q8gOkUrfh?= =?us-ascii?Q?8hjE/iFo4Q9mrAFBJt4kSQrhr8+Qw6dX2ik9IU0n7ktMouTKbRzfNLTazHEs?= =?us-ascii?Q?s1u+L6OkfCBiumR9exQZQ7+i5kOAcPPqJ4gqriRSGW49tZD3p0SFg2rdp0OS?= =?us-ascii?Q?ZN1m1ohsoVCKAj6DklB7vA0PcXrqJrVuYq1Z2DtnIvV1T+yWParNAOxzBhhl?= =?us-ascii?Q?KhWG/xpkYK7l4TuknAz4NoaLGML6MS/tPWNDJtaoxL/1VRC2ZsxUdXHRf7FH?= =?us-ascii?Q?ZfF6fAw31KVW1+NdkAOJEdaXnra+ldaW2kwm7XyL//p0V7noP18WKcojg7jb?= =?us-ascii?Q?YL/QKpj1xeWkAjyP2m9knMsbmiEmH70AW9uW5vgDDMlBOJKzfugnwjVt5LAI?= =?us-ascii?Q?fjtzJ7PsmoKWrB2aP1E7gWrGpdYcXGWoGABCDg0niJxm+klQWuI7B5dHymLh?= =?us-ascii?Q?RkBDyfw2r1mujhB62KxTcwE93uk95RE8Be8X4FIbTL/ihXjNETnpOoC3dnSs?= =?us-ascii?Q?BH9nYuQvqsUuomqTXLTlK4Jlgv+0E2g2NAHD5k8uztbynNto+wceu5X4ZwUG?= =?us-ascii?Q?FOXU1Ikkv3//eD/GdIHf7x+LTD9V8i0h20eJbi4xbr3kHbeaxm/CL+11AZ6W?= =?us-ascii?Q?uOII0UQWa8W3ByE0PBrdtq7gEI537rsow1eY6OnVLb1emg+QjKs9WvOt6TH2?= =?us-ascii?Q?w9783fj9z7xjbJFyn+zzcWuNXV32GKRlJBpD20PGPQOzxYVo+g=3D=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PAVPR03MB8969.eurprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(7416014)(376014)(7053199007);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?8Abf3ORcMIyGaPd9j65/rhkXa9Vrv6skM5LRoJxuY+z+16U9Th+PTAH47WHe?= =?us-ascii?Q?f+ZcQPli/+YOL9yJQu4nvFgmxMRYzM8R7d6D5mGeGiZNFpTTfplK+dojGO22?= =?us-ascii?Q?GDgkPkxMGO0veSS5a8oRAtl3vMs3uV3dL1BBAjj9eyQ00ZeX7eS2Mzoh4E9c?= =?us-ascii?Q?eS+FNkNaHtsGwR9l0S58jstLlHuIVJKLdAvfZ027BvxEHOsLajOZh/6Zod0D?= =?us-ascii?Q?JAAjHqQZaqx6P7dwM2FWgx83ZHMCDkr9L/RvAMCH/m1OYpOfC6lxmDIDFlwT?= =?us-ascii?Q?0L9QM71ifK0tFBok+4OjntU0a+E6YQ5mfjFzKNFfHjcNKWCalH9SrBGD4km/?= =?us-ascii?Q?/xlTMAzcbS4aevVmkBglNaMu5cxamikvqvLccGijM/TWSNTVkdDkdkK6tQ+E?= =?us-ascii?Q?ADYZYhFWywzoxxV9Tlcqi/SebVDXEcyGH31bDH/Z8CaHcSupL1nvMrA393RP?= =?us-ascii?Q?w2eavnj0wEdv0/qe3gJymi1OufXOvtqvaliwmP5OT+KUhY96WWJmf0221gKr?= =?us-ascii?Q?IweYjOEiFkn3aJivohY7Ym1C8UYHoEk7AM7AODMmKHRtW5TsYCrAzyM22Q1Y?= =?us-ascii?Q?aHeeZ5dgX5ihA5QTpMp7dQfS9iiEbb00nHLSAkRjRMsMqj4SsGozUUSWaPi3?= =?us-ascii?Q?14cKSF22WNNqPKcAp+qDrfFoIpvFhaVHfxKoStgsoT3k47OmnHBTZnRDkyg8?= =?us-ascii?Q?aWJtXEoumKxltE6eUNuOLgxIamGtWAbam/DPypTqOIf2mzUSg0xYaAwYTEp6?= =?us-ascii?Q?zGXKjtglnQSRVnTs1mpeIWqKjtN6rgXtBhybbHZez7KuBWfoDgeFK8Ax+8Sp?= =?us-ascii?Q?rRcvx+pJ5M9nrvt2/GpsJ1fdQjYauIJBHIys6WNacel+rX1rLX5XM7hUfp8/?= =?us-ascii?Q?sSyk7xtF/PVJQrLOzAK9fLOUnbBWFd5fP//Gg+FVJ6YwA36j+wjPLY1ONYac?= =?us-ascii?Q?lfso4jL8fQLyoRmzKhyoex+21q9CZkg6bRp8eX9tqk/gW5aoIPVhckoZ+G+W?= =?us-ascii?Q?QSaII6wgwm9K0G2XpHSWuqHB8zrHvJgUjB8VFTJT3DR5CFD1oUbr+69qYxEp?= =?us-ascii?Q?IYiawrpat9klnVOcGDnEQzCXmGM+TClCi1Uz6X/h8yU59WOs3ERuRl1Ez0G9?= =?us-ascii?Q?kGWXrHPdB1H313fDIKuOFcK1jBtrm7BcPi/JX2cPxfOaiAtoikSE6Go27zUq?= =?us-ascii?Q?1pTB5iqWIFYVokY8pA1ZYW4/MO29ikeUJTz6kA1wjVzNpi4oFbc/pT+NGY4w?= =?us-ascii?Q?f7V1dkHwLEadlsuVcYaffrqM/tDth+d7aAhXdhFtilleL0d6niXX0dgpcYUC?= =?us-ascii?Q?nsPvKNs7BbA6deCYEJY3qkdWfd3bw+24HkBDC/CSAyHSaL7g5yMxKYvH0soH?= =?us-ascii?Q?eIFB74/PryIVbK+/D4NCqUbRu1L2VI6XWese19s8JHaWwTpOdMJwb1/5UoWr?= =?us-ascii?Q?XLEBxsZlQVUnfvB3LXNHERJs/pMzlBZKqByKYVCzSHIA34t+TH+zUgSwk6XB?= =?us-ascii?Q?drku9XR8LYH4mxKhYTCneuH3Uftu1OUzU99aRwvWM0TD3eZsWuNVCUDHn9O6?= =?us-ascii?Q?BN3IjlL9j36gxOkzBmDsrpv0Crt8CDS9CcSZu+JLZhZUR6jZWWSwryf8Emh7?= =?us-ascii?Q?vQ=3D=3D?= X-OriginatorOrg: santannapisa.it X-MS-Exchange-CrossTenant-Network-Message-Id: ac0b1f89-7d3a-4d20-0c2f-08de12d3ae76 X-MS-Exchange-CrossTenant-AuthSource: PAVPR03MB8969.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Oct 2025 08:02:30.9527 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: d97360e3-138d-4b5f-956f-a646c364a01e X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: rtL6/ul/aTb2zEXY6vsGcGkFlQ9fzJkw9k0ld7jY7XmudusNmjK8k1j4EhJnG4GLvlEU3oP8sTcfw7lzCgbKkIctyBuim54fEzw3jocwygY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR03MB10149 Hi Juri, On Mon, 20 Oct 2025 11:40:22 +0200 Juri Lelli wrote: [...] > > > - The first patch which removed fair-servers' bandwidth > > > accounting has been removed, as it was deemed wrong. You can find > > > the last version of this removed patch, just for history reasons, > > > here: > > > https://lore.kernel.org/all/20250903114448.664452-1-yurand2000@gmail.com/ > > > > > > > Peter wasn't indeed happy with that patch, but I am not sure we > > finished that discussion. Both myself and Luca had further > > objections to what Peter said, but not further replies after (which > > can very well be a sign that he is still adamnt in saying no go > > away :). Peter? > > > > https://lore.kernel.org/lkml/aLk9BNnFYZ3bhVAE@jlelli-thinkpadt14gen4.remote.csb/ > > https://lore.kernel.org/lkml/20250904091217.78de3dde@luca64/ > > I had a quick chat with Peter on IRC about this. We now seem to agree > that a third option would be to move to explicitly account > dl-server(s), correspondingly moving from a 95% to 100% limit. That > would also make our life easier in the future with additional > dl-servers (e.g. scx-server). > > What do you think? This looks like another good solution, thanks! So, if I understand well with this approach /proc/sys/kernel/sched_rt_{runtime, period}_us would be set to 100% as a default, right? It is often useful to know what is the maximum CPU utilization that can be guaranteed to real-time tasks... With this approach, it would be 100% - , but this can change when scx servers are added... What about making this information available to userspace programs? (maybe /proc/sys/kernel/sched_rt_{runtime, period}_us could provide such information? Or is it better to add a new interface?) Thanks, Luca