From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM12-DM6-obe.outbound.protection.outlook.com (mail-dm6nam12on2085.outbound.protection.outlook.com [40.107.243.85]) (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 5C6211E49E for ; Wed, 25 Sep 2024 04:54:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.243.85 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727240088; cv=fail; b=r+AzanhycQ1AZNmxMoa+C8KeQggfszGpLo8y+E3mZq83zEAXLrvzg+UU5c96nzj0d3yzu1pu83OoPycy5eKdH/l3B3YKAlq7DM6JINoGwihvsMGJNyAj43meFBuAaSXOOB3EYFHhp0a/2Bb9cCJLcxgMe2xUIGLBrUQK/avm25w= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727240088; c=relaxed/simple; bh=S9oSRoX0KbKWdJTuK3ffAYvkkZfioj2v/nVxVX+cffc=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=b2tkGcQn/keeT80RkOb/pD13s23+X/S4xAzHSFPMdL5HV7pzWGzj3xDra87dywZ4vV3QQV+l+hq/gpVrefRCVwhYizs+wZ2G5I0JvAjL+9SJGaNg7WxvSzx4efEaJOrR8VaJSNLTXpG0y76BauBwDsENHvF06Zwq7TboS4mYPLA= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=y9tc/8Tb; arc=fail smtp.client-ip=40.107.243.85 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="y9tc/8Tb" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=kL95d2baGkvtQpvUM/vSLb/OWKJT/BYFCLVU1N/pmeqWrluJHuQYvXyhTCegonA7zLwhi3AUrtU9IRGnDbDAg+FrGJf97dmAUlW/3dH8v4tJLZu0G4tRZagqPk2q8JTzngi5pBkbTp+4T7g0TU7/zTpg2fopj8gjhCH85QgqaDs5fSUKAXRoVFN1wEcapDRSXMR94osN1wdHLAAG/Q/+dv8n4Pko1Wizl6A21xIAZ42E61fpX861poyMtEln/gsIT7xkC6eBFsuJPmVomhh9D8Q3ngUEu9aHisTLIN16NVdW8BKU7m6zcmGy+5UgrxwFZwkgR+RveoAMtqLBO6MWSQ== 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=h7jHa4wg2C5ibLyV+2jdJiJNcqYb8fPczHD02toZ3+k=; b=d7+p8P5H+6ClduLg31R+NqD+Avcc9Gq//WAnbuWFdDyh8cHlJI/Gx7bHtPmF8vCmpOEYdhoZT9g5tMoWbhV+kUz7eklkeQ6zVmkRnJ5/zPOeoT5LNd6h25wxdlt2+Fme1wb8RRNhQbKmges0/a0OjVY/BakIfQleUL43NgKxkzNvPljViVbBgGfK/ADgQUFwUP3hwtvmKXoIjXwYTfIvw6XibnjYBXSgF18pMlKfbaJCFB/9fsR+5iD82zYrTtHR8Yh8JqzozQmPg9z8gWzeyahfNNiyEJqDjZk3HirwmZ6uh64lwQORfmpKW9mjGP7z4E+66VrcgfjkUq4H0hbheg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 165.204.84.17) smtp.rcpttodomain=gmail.com smtp.mailfrom=amd.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=amd.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=h7jHa4wg2C5ibLyV+2jdJiJNcqYb8fPczHD02toZ3+k=; b=y9tc/8Tbkfl6pfJGycNxVwkQy86UQJugG0TyDuH4gE9LZUE9DEcCPeuNnEqyzrgsXstDXupwAfx78oKLYiRPD1/Fq341KeGPEUHBhh8zfXV3wMN5lt0EoU2cMhy3dyywviAwXZa5ldNZdsGRXGEZ2hxnYRHcIpDogdIrNX/iz24= Received: from SN6PR16CA0050.namprd16.prod.outlook.com (2603:10b6:805:ca::27) by SA1PR12MB6995.namprd12.prod.outlook.com (2603:10b6:806:24e::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7982.25; Wed, 25 Sep 2024 04:54:41 +0000 Received: from SN1PEPF0002BA51.namprd03.prod.outlook.com (2603:10b6:805:ca:cafe::9f) by SN6PR16CA0050.outlook.office365.com (2603:10b6:805:ca::27) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7982.23 via Frontend Transport; Wed, 25 Sep 2024 04:54:41 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by SN1PEPF0002BA51.mail.protection.outlook.com (10.167.242.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8005.15 via Frontend Transport; Wed, 25 Sep 2024 04:54:41 +0000 Received: from [10.136.36.144] (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Tue, 24 Sep 2024 23:54:37 -0500 Message-ID: Date: Wed, 25 Sep 2024 10:24:35 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH] sched/eevdf: Fix wakeup-preempt by checking cfs_rq->nr_running Content-Language: en-US To: Chen Yu , Chen Yu CC: Peter Zijlstra , Dietmar Eggemann , Steven Rostedt , Valentin Schneider , Chunxin Zang , , Oliver Sang , Ingo Molnar , Juri Lelli , Vincent Guittot References: <20240923072156.343623-1-yu.c.chen@intel.com> <3c969a0b-812e-dedd-b9ed-6378f61d5735@amd.com> From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002BA51:EE_|SA1PR12MB6995:EE_ X-MS-Office365-Filtering-Correlation-Id: 1b5f68c9-5a0f-4b80-8849-08dcdd1e2a83 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|82310400026|376014|7416014|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?LzdjNW1KU0NXOWpUekR4MFQrMjJRKzZ5bTZIVE5UQ0UxWmVFVGxsK1F5R04x?= =?utf-8?B?MG5oOUpzNmd3OG5WZDFaamxqK015WHZCajdiVEZmUFgrQjVEaFZhVmZZbmVw?= =?utf-8?B?TiswVjM2WURQdzdIZm13NG9ZdWlrSzVHanVISGdqcGVTTERZSlp0T25Ub1hG?= =?utf-8?B?NjZNUU9pVGlLSGlab3R6dzRCTEIwUnRScFhKSXR6M3hCWjNhSm1KVkxHTFJH?= =?utf-8?B?RXAvbUdXb1VrQzBUWmd0OERweVQ2NEVxTnNDYlNOU0F3dHhWZ1F4aVBjcVdJ?= =?utf-8?B?TktDdzVCUWR6dVFWeGJmK1FlQWtJU2hFcUxqbkd4dEMzaWlXcEFrekkrWEhF?= =?utf-8?B?N2E0aWlMeUR6UC9pUVEyYmZKa0FYeU42cU0zcDhoYm44Tlc1SU9JN0lkZ0My?= =?utf-8?B?WXhLbDlmODg5V0t1cWgwemhLU2hzTzEvRHlsL1E1NUgrTktENUhvNjJZdXBS?= =?utf-8?B?b3B4V20rOFhNR0ZXcEdTdE40bnlockkxanlVS2E5c3cvTGFPZExCQVQ2NWJ0?= =?utf-8?B?a2dvTVFXWUwyVUhyYnZQL1Y3amFIUGFlRnVUUkxzaVphQ0VmUFZPNkpsRXQ0?= =?utf-8?B?UGtablpZVCtLZTJ4YThpdFNucU44UzVnSUJaTXdsN3hTMmFlQTZQZWdqSko1?= =?utf-8?B?VUdsVExsWEZRZXpBL2kydFhjNmorczl0bEk0WDRmaHJ3bE83bElUSWZwckJ2?= =?utf-8?B?Q2VlK2dSK0ltQzJ0cHFoWEY5ekVia0d5dE5sMmcxbmk3YXRaQkFFYWdUWmJ4?= =?utf-8?B?czlMTEgycmt3dkhOaGVwS0dVRmphWjh5VDZNZmpmV25pNEpoejJFcTJIQmlM?= =?utf-8?B?c3lxbllsdzBmbWhYeXRBU056NjZhcDVmRkgzQnlWbXRWYUxiUnZUUldZTWkv?= =?utf-8?B?Vm9Ca3ZXWlBycGhHSW1peUFpSW16QlA4QVR0OXc1YUx2TXRMdEdMTGZHVGRX?= =?utf-8?B?alNabzdwNGRoZzVZMDFtTVhnWkFHbkpsUy9rVUhSSlhRTDRQL0poSEJmWk9G?= =?utf-8?B?YVJiOWlIZVpsK3FjcU1CUXR5QTFlRlpsaU1jRVpUTGoyankxSWZzQ1NhSGhX?= =?utf-8?B?U3lHOEhFTmNrNHJKZTQ2MjJRUXpocjdqN0Q4WkFsVmFuRUJjSEZrcmUvZFN3?= =?utf-8?B?UFpuN2ZaMm5SS1AvQUN5ZTduZVQ2TjA3WktTMGNzVWkvSzVCTWNLOGJNb2RU?= =?utf-8?B?S2lQbkZwT3gvOGZoaXVlektJR2w1ckJ0ZzZBMWQ2Rzl0aktOVFh1TFQ3RHU1?= =?utf-8?B?cHBBZ3JKMWVsN0xVbnpyK3JkUTdyalZWYzZoRnRxTFlUckJJMGVRTXhYTW1m?= =?utf-8?B?OUlneTM5ZEcwVGtlS1kzNHdVMVF6c2NXMkMvdWJzU3pIU21ERWhEWUh3TUp3?= =?utf-8?B?bDdjQ0JOY0hPRXJDN2d4T2FkMFJITmRjQ3R6RWRFcW1GSkR6NmtKS3dxYkUz?= =?utf-8?B?Y3dSdXlFdkliMXpqbTZRUm5EbXNsOCs4L0gycVVHakVJdGc1VnNBLzdaa0xJ?= =?utf-8?B?R0ppLy9xZFF5K2JYVTFWZFNGcUpxQSt1REJRUGQ2VVJNOWQyM2tPZEhoZnd1?= =?utf-8?B?ZDhjbU0yTUpNZGxwYjZkaDBZb09xRVFkMi9yQUhKd0VzNVBXK0dRRnpUeW1z?= =?utf-8?B?anBsUXZ6bEFqblNVVythQnorV3dURzNuNyswV0NBcXE3WEQ5YktUaFFYQmF3?= =?utf-8?B?cmZFVk9ZRkJpbHB2UDhtWThscGNKRGdqNnI5UkJiYXRTVFpOWjNjS3pSRlQ1?= =?utf-8?B?YzVzZnpSV2NnRXlHRFJrVGdSbzBoRWp5MURoaUQyZG5PWmlZTGE3MTBJaWxC?= =?utf-8?B?dzU2amRKL1hUbmVxdWhsaHE4dWZsbTNTeFRhMHdYM3loMlVrajV1SDJleHBR?= =?utf-8?B?eVluMVhHbUxDZGJ5M2I1UHB6enFTdDhWS2JEdllETFdyVSs3NXpuZnQ2d05V?= =?utf-8?Q?IBC14lPBXg5AUEMS7r9o1WqLqZOfx+VM?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700013)(82310400026)(376014)(7416014)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Sep 2024 04:54:41.0850 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1b5f68c9-5a0f-4b80-8849-08dcdd1e2a83 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002BA51.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB6995 Hello Chenyu, On 9/24/2024 6:40 PM, Chen Yu wrote: > [..snip..] >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index 225b31aaee55..2859fc7e2da2 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -1025,7 +1025,7 @@ static bool update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se) >>> /* >>> * The task has consumed its request, reschedule. >>> */ >>> - return true; >>> + return (cfs_rq->nr_running > 1); >> >> Was there a strong reason why Peter decided to use "rq->nr_running" >> instead of "cfs_rq->nr_running" with PREEMPT_SHORT in update_curr()? >> >> I wonder if it was to force a pick_next_task() cycle to dequeue a >> possibly delayed entity >> but AFAICT, "cfs_rq->nr_running" should >> account for the delayed entity still on the cfs_rq and perhaps the >> early return in update_curr() can just be changed to use >> "cfs_rq->nr_running". Not sure if I'm missing something trivial. >> > 85e511df3cec changes > if (cfs_rq->nr_running > 1) resched > to > if (rq->nr_running == 1) not_resched > which does lower the bar to trigger resched > > Yes, I think your proposal make sense, the resched should only > be triggered between 2 cfs tasks, > and the restore to update_deadline() is not needed, something like below > in update_curr() could also work: > > if (cfs_rq->nr_running == 1) > return; That seems better IMO unless there was a strong reason for the original change to use rq->nr_running :) > > thanks, > Chenyu -- Thanks and Regards, Prateek