From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=pass header.oldest-pass=0 smtp.remote-ip=52.101.56.68 ARC-Seal: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=pass; t=1792447432; b=5IXpwxyBeID0rtPOAM0qVckPdMc9QPeZCn1yErpl5a1lqwdiYu5q1PT+BCf2zllBzDOn CvGnxasRDwuz7VdLKJThg6At1W6MqTWx9PCeDX6Ig5g7dysLR8n36M7Zvx7vLw7RSOp0g oHGZY5YHDlhS2IuRiFH0GqD8lYtvNR7hgeHwId9B6dZUffxiWA3aayhy8D8Bplk4KiXcA KzeADCSqM1mC8IYO94Oqs5bzjGuBeREL90jI7Znl32vFalpwr4rT0m3M2XS4nhUCKEyqP iFqeyDr0PFqzROh9IVUF25WpwL3RV1K8sGS0KwTfQXLmc23RFd0u1XzLp0T4uQgPi7g== ARC-Message-Signature: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792447432; h=DMARC-Filter:DKIM-Signature:Received:Received:Date:From:To:Cc: Subject:Message-ID:References:Content-Type:Content-Disposition: In-Reply-To:X-ClientProxiedBy:MIME-Version:X-MS-PublicTrafficType: X-MS-TrafficTypeDiagnostic:X-MS-Office365-Filtering-Correlation-Id: X-MS-Exchange-SenderADCheck:X-MS-Exchange-AntiSpam-Relay: X-Microsoft-Antispam:X-Microsoft-Antispam-Message-Info: X-Forefront-Antispam-Report: X-MS-Exchange-AntiSpam-MessageData-ChunkCount: X-MS-Exchange-AntiSpam-MessageData-0:X-OriginatorOrg: X-MS-Exchange-CrossTenant-Network-Message-Id: X-MS-Exchange-CrossTenant-AuthSource:X-MS-Exchange-CrossTenant-AuthAs: X-MS-Exchange-CrossTenant-OriginalArrivalTime: X-MS-Exchange-CrossTenant-FromEntityHeader: X-MS-Exchange-CrossTenant-Id:X-MS-Exchange-CrossTenant-MailboxType: X-MS-Exchange-CrossTenant-UserPrincipalName: X-MS-Exchange-Transport-CrossTenantHeadersStamped; bh=q1QK71bn+AbLncP9hug/0LrTeFF1y50arouKOUky+yg=; b=0gT+uCSbwChJwo5ebPvhkbvPqVtG//vaJ17rKtWroJ2xgL4BpBprcD4txyLcaYNFNipS lQL3YIzRX/NdlcjCEPOO941ers11tgXt8NFy7+s1AcZg9mGRKNRTnYNJCZmCwNf5+ss16 MnNQcO213pUl1JRLdtguyLL657zHYLBo6O6GV+pS3TPhUd3s5eFhrc0Ke9nHyWiMdHt2i ki8d7hGzg0XnLPE0N1BhmmhfahpC33pXOHWQ0qTEXgFqFmO7kHWIA8Qgbmkf1Hn+xXjWB tCVaU2zt9qSd6SvVJZhAUKPi5QeaHX8xsDqqwfgg8uCBTdtDGq5rrTUYH6IyoB6WQ/g== ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256 header.s=selector2 header.b=ad79eAoy; arc=pass header.oldest-pass=0 smtp.remote-ip=52.101.56.68 Received: from BN1PR04CU002.outbound.protection.outlook.com (mail-eastus2azon11010068.outbound.protection.outlook.com [52.101.56.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (secp384r1) server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28F4D606A31C for ; Mon, 19 Oct 2026 22:03:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 28F4D606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256 header.s=selector2 header.b=ad79eAoy ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=hjDRKM3o06gYzCESVXr71dynhv0RvMuq5fTkTj/xjO/I/bInxBq8YGPoEj9sJ5FFVFkfepVo3mQQE0CW2eow/8/HtdTMLDbjKYSOcFXRNrDY0U2sb4jqBWoxWxn+4FFkfVxdfobjPTxeS3guJHAyJNeJQG6tGErediqXDBPTMANl40QOLQed1XTyo5Ou/DbQGrr6vi3Fj10EhzEPCL+eyhE3X7NNXl6yLlKHnIPysOxm7uWnXHVxrko0TDtISY+Kf5rJVpKvZpRMxyVwQwmvursP4T3JuKhIhJE8i0OEpsOcuRufhW34YZqgEIwVkuwtINvqbOjgaVbm+mzdEPo5zw== 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=q1QK71bn+AbLncP9hug/0LrTeFF1y50arouKOUky+yg=; b=cI7WU6za94NrO0bKifBiO6WSEQpKS6+ippNMKKraANan0XSgq6sbmik0eYBO0WWMn22AGBvPEf8Myu/EnJgqHpZ/EHAwLvPNt4zofd0uXQ+gI7L1Wr3fa47qXS+VQVOIKY8jlh1KXwu/DYy2U4EgGa63H+yVjUPM8UolACUt5N7hO1UP0tdRp5msUGJrLCvBJQ728797mytKEokAcBFHAJUgFhY4qqHusQv3KCxRD5jGUqpZi0eV2PafGPk7rH46X9JKiUVp7vvgZQSeN1Aj66Lb+KypKVr6Q+xK6nPE8lcGrFCbIE4AcJMG2W7RDXnWSK8/rO6hRHtWgHJ+9AdDhQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=q1QK71bn+AbLncP9hug/0LrTeFF1y50arouKOUky+yg=; b=ad79eAoyiszXd1A6t2MMTrgRBhd3uoM0xSoUNhGdCqIJcA94QtqgjaPl+3Bg9q/wZQdghzcmnw25YQlrFYoeCJ2FnNek5R1mSBTj25+UQuHHFRaxIohuZiZ71EB/51YeD4KofgEUJoqstRyNwk5HWWNaIDHAogM2u3F7prxAclG91aP1NdVSS7qJGI1cx1K6hYdXW/p/oWuhHMwTJbZ+6x2xNpXK1MRULBxAptLBlru7QHjwr0mchgu6qGk9sM4WRj9u2VeAdZRJE954ySd8RPOtH2jfDgmWir/eK4OkhHfq3DsUUp+XCjSgHHE4kskNgYEZr4WUXIw7yiF8dsXSMg== Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from BL1PR12MB5174.namprd12.prod.outlook.com (2603:10b6:208:31c::19) by CYYPR12MB8751.namprd12.prod.outlook.com (2603:10b6:930:ba::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.522.19; Mon, 19 Oct 2026 22:03:48 +0000 Received: from BL1PR12MB5174.namprd12.prod.outlook.com ([fe80::58de:822b:868:96e9]) by BL1PR12MB5174.namprd12.prod.outlook.com ([fe80::58de:822b:868:96e9%6]) with mapi id 15.21.0522.017; Mon, 19 Oct 2026 22:03:48 +0000 Date: Tue, 20 Oct 2026 00:03:39 +0200 From: Andrea Righi To: Tejun Heo Cc: sched-ext@lists.linux.dev, David Vernet , Changwoo Min , Emil Tsalapatis , David Dai , linux-kernel@vger.kernel.org Subject: Re: [PATCHSET sched_ext/for-7.5] sched_ext: scx_qmap: Drop the compat code and fix a lowpri starvation Message-ID: References: <20261019213221.2919481-1-tj@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: ZR0P278CA0036.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:1c::23) To BL1PR12MB5174.namprd12.prod.outlook.com (2603:10b6:208:31c::19) X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL1PR12MB5174:EE_|CYYPR12MB8751:EE_ X-MS-Office365-Filtering-Correlation-Id: 22e0cb81-08b5-4d17-a683-08df2e2cd9f2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|376014|1800799024|366016|22082099003|18002099003|10067099003|11063799006|4143699003|56012099006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BL1PR12MB5174.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(23010399003)(376014)(1800799024)(366016)(22082099003)(18002099003)(10067099003)(11063799006)(4143699003)(56012099006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?OCs+L/9z79o1Yae2cLVF3ty8qucsYy70HEuPJp3tMeRawHsDyiOy2NKo2rru?= =?us-ascii?Q?y+xpiChgVvoiBwlyT39gauv5/V9LxOtpjpUm3nX6pSfERVo7t9ZJ7VBwQLMC?= =?us-ascii?Q?/HxN49m8/F0gaYgJY8a7ZGIkFVddm0hih9hiXSuTdcpKjHAYAZlr2hmoDV0j?= =?us-ascii?Q?9Vkz8FRkr9xb8cuM+1LNzu9xYOE3FkoonjPhSFV3A0BfMMVel7qGxsHPnwJ6?= =?us-ascii?Q?IbLqQn4oEbc534PzPhRD1ZZNN7BSveIx1cbc88rw25xHfftwksUlgJxKXrfw?= =?us-ascii?Q?DBTvD0tY9FJWcQUvuHX2+GGOSLi043YOt77SvnN9TqUAmpUjbjg5YrO81pPx?= =?us-ascii?Q?j+ymlbo0nODUpeacNrBv4ELkTBDTQDCXrawStxfG4bs4trvKL0iIuoK18HOp?= =?us-ascii?Q?V9AGHidsYnHER+xS4Q1XCw+J+TIKR0cGVfvNd377oMXi5JeGcNk+oU9ACTBp?= =?us-ascii?Q?rf4kghGu0AbGL+nlpa7x2+rSo8860Lvj3p4XwHC+egtf75LHp+74XSXORNam?= =?us-ascii?Q?pikHERTFng1vTGwXJtlXP+kc9s/uHBMy1G+uKnmB0ZHgMrntbEJ90D1g7KH/?= =?us-ascii?Q?nBtLDcPd7u8VGIoeooqBqHgm36GWN1uopeXztV1Immqch/VWxrVHG5hlBUMl?= =?us-ascii?Q?A535xbIF8tmFlThLKcZ0ue8AnyJNb99jnjsa8lcri3iFUGyugjMyIoWv6+VH?= =?us-ascii?Q?SVEU5r26JUaMwwzF8A1PJz3VicdpAdzlMCtvqXdYyIu45pdnBJ6HNpE3mj0i?= =?us-ascii?Q?qrLjIrrw7GG6jkmFoiJgIvBMuQW+GAFVRrzE2FDXQ8xmBw/wddtbtakKfm/b?= =?us-ascii?Q?obeVseMabPpNXRUXnJEfSUJQqzDZUtX2gxe8IL0DOgchOu9K/h28nsKe5ebd?= =?us-ascii?Q?zSyd7OMK2FjhF1Y3v+v4zQaIiuMyuMdgLYxArVgoee8zRocuIiT7KDwkBYcb?= =?us-ascii?Q?Y2VHGzC4wDDSa52kX45rRzUiVbQIHugjr23ADbon6qlXx8Pa+mwj84NCVYEo?= =?us-ascii?Q?Xzktmoc1eAyAFyp5USHalHv/DNi3xZNzG/9h6409SclTivSOhJBmIv7Wkc+E?= =?us-ascii?Q?GHLA9XrnDcinoYh/UzWBC4Y1oIbFgi7+S9d+BJrYkMp4g6ZiSYMrK8dL3lhR?= =?us-ascii?Q?CB3JK+hRKkX6tDO76dL0WdOo3TWqC1HDm1vimNaZLCbFNykju5V1Q/XY/NRf?= =?us-ascii?Q?nqYZNBdnoYTFwxbE3cfjBNJYSaihXeFYllua1ug9EHRhw312HPrYus3b2FAN?= =?us-ascii?Q?iD4D29EGfqa99uwwBqtPDIKeHabynYp4WdDlzer/riH9oTFKQ2IHnV2pNPm0?= =?us-ascii?Q?y8QCowtzcu6+XzdHXSr0lkMn5vYPgY4KquPX8ySTid3x9kVQj+sXEQVAJXA3?= =?us-ascii?Q?ueKI/Vqq5EVca7xPPs4NUyAcyfTuhuBwh2QNsW35erHHKixXCn4JLKkHqzI8?= =?us-ascii?Q?oTSgIz3wE2qXB+R0rOF7XHP4nOuctM0Z17sQ+leT6lFjdrwfvqlvFBklTQgd?= =?us-ascii?Q?TKmEsta48AtNyLUuFJXv9YA7/GJkUflKkPXmOuf9tYDtjUoQfJHHGgFJIk8f?= =?us-ascii?Q?tWLDZGUdIRf4r+vGAWElNtpR18kJdDrR8SPIpEe70qXYD6I7dA4IXo4t3l6V?= =?us-ascii?Q?/zZnpfk3AOyiBy7ss5e2GxNAKWs/HbMUIdZXUdhVybnM3KFikvf99lF4wxz6?= =?us-ascii?Q?79RPFKb2Dmvfv+KArpB2l6N+idWUbAVu8dwDmXvBKwhmdMzNIcAsP1+Ed/CS?= =?us-ascii?Q?OLExBlIf6Q=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 22e0cb81-08b5-4d17-a683-08df2e2cd9f2 X-MS-Exchange-CrossTenant-AuthSource: BL1PR12MB5174.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Oct 2026 22:03:48.0902 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: q3TtWBRVNUruuX2HoOfx01MQY77JcZtQYuIlwwUSizRoDgPapW5bYpi+LqU7FjIRd5eopkkt8lGSdAzD9m1iUw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR12MB8751 On Tue, Oct 20, 2026 at 12:00:29AM +0200, Andrea Righi wrote: > On Mon, Oct 19, 2026 at 11:32:19AM -1000, Tejun Heo wrote: > > Hello, > > > > scx_qmap is often used to exercise sched_ext features as they land and > > already requires the kernel it ships with, so its compat code only keeps > > untested fallbacks around. The first patch drops it. > > > > The second fixes scx_qmap's lowpri path. Nice 19 tasks coming back from > > LOWPRI_DSQ go to SHARED_DSQ, which is consumed ahead of the FIFOs, so enough > > nice 19 CPU hogs starve every other task until the watchdog ejects the > > scheduler. They now go to their FIFO instead. > > > > Tested with root and sub-scheduler instances under nice 0 and nice 19 CPU > > hogs. Without the fix, the root is ejected within seconds. With it, the runs > > complete and the FIFOs keep being dispatched. > > > > Based on sched_ext/for-7.4-fixes (ff343a94e44d). > > > > This patchset contains the following 2 patches. > > > > 0001 sched_ext: scx_qmap: Drop the compat code > > 0002 sched_ext: scx_qmap: Queue re-enqueued lowpri tasks on their FIFO > > Both look good to me. > > Reviewed-by: Andrea Righi Oh... and as I sent this, I just noticed a small nit, there's still one compat in scx_qmap.c: ppt = __COMPAT_ENUM_OR_ZERO("scx_consts", "SCX_RESCUE_DISABLE"); We can probably drop this as well. Thanks, -Andrea