From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BL2PR02CU003.outbound.protection.outlook.com (mail-eastusazon11011061.outbound.protection.outlook.com [52.101.52.61]) (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 D6C4332720D for ; Tue, 28 Apr 2026 16:17:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.52.61 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777393052; cv=fail; b=AIhC4bZvHLjtvwCCcUTHiDD7lxhufmyk1W1ZsmizjFqTZygc54w/8lg/jsTlAzfR64gcoBnFx7du/l/oEeC0pRcTyLB8Xck3n3oZyqGmHj1g895ccHwS1sbqGeh/DrbU0Bn01tFcj+8KOo/u47Bujkl9sry3fckgrnuGD4yU3u8= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777393052; c=relaxed/simple; bh=Z7Wjgp+ltsTyjVu5HVkYBXOO9FZNBy+xsZWP1IwPGi4=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=MyU8KLv1e+m3XqmTfUbD4r2rRvHuCLY/1K5stn9jimraOeNc1VjsWGHTTGyVBLgU4qJ6VGW0Mq/C+nw6v3hTi01SN6kNucqCwbnyMWyIVhlZ+lJEofTkTfYBUKosfzYTFY5vT2j+5NwIxP7N4MvumPJGetYpTnVE3exL+eovxlA= 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=MoYa7Hlt; arc=fail smtp.client-ip=52.101.52.61 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="MoYa7Hlt" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=shW/Y9QXr9nCtVzaJNwycRaFylo8fB5lDQvT4DXm9K9S5DzVNVf1flhimSqfcWaWD6X1E189Nn1P2TKHJiRZbawKyxVcIJntAb8sPtBdEU5N7LlpczxSNq+0dTMFwPUgsHmHOhGu5yw/03F80yM8LsCxWvKrcdqIgTyiuttCnqXkDkYWt0KiWHy8yWmhFHt7dC42Xr994DoWOUtewfdFKZLy3E+MkLSuM84oG2G4/1ZgiaNygrXGe4l0QWxhj2LZ7Mxv47PRv1Zg6UvUcpBkg5ky+vwWzVIZ/ohjmfAnpLfBvNU5Fl2nr3DNt6QfbW9ZU4Y2rumzysa+U5TatSk5kA== 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=mhYcPyM/PcAtNR4EL5sBWmtf45bS/ZtkTsBJbxJiiOI=; b=gfOhVRjPdCN7B8IYGaVEE0KwmvQjpKxnLOqHU/BRJh5CF3tox96yXdMk6nXGXjlGL0TsaNBT7sbq33lauYsLssDnWoSQ9bfcPTyHJKYFGqftny5bHtI7c6SrEZvTJAouHfDyn5ypnWygLBPv/QI5Umhr9YnxEIevjpHGDcUBRoqgAUkX4jem4j6OMYWyvukkfGpG9ePJ8BhC6QldAILzKrpGM4d6b06wuzA+Uwxa45VblZHZdfzz4dGoxND7uAD7Rf3gpkzTFVL6D2vKpd8OzBZ3E0rhVtC0J6GPV+29zUO0JkHbJAUsEZjRrwfFqgdnPX7JYaCk0E5RnDSN9IpuLA== 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=mhYcPyM/PcAtNR4EL5sBWmtf45bS/ZtkTsBJbxJiiOI=; b=MoYa7Hlt5gedjiqxr3lHnh6PkA0wWJCZmffQO/DyYVFzqu2foyG5H0N4dHzmCsrrKRUJkxxM9h47EP+q7sZSVYtVisWfv72Lapf6G/YJkLXFdyt1007/2rSaIBlhR7iHWHjuMwE+U0ABNvtjRT1JRuLGxCgiQGkP/Tbxn0oomv4= Received: from BY1P220CA0045.NAMP220.PROD.OUTLOOK.COM (2603:10b6:a03:59e::14) by MW4PR12MB7191.namprd12.prod.outlook.com (2603:10b6:303:22d::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9870.17; Tue, 28 Apr 2026 16:17:23 +0000 Received: from CO1PEPF00012E7E.namprd03.prod.outlook.com (2603:10b6:a03:59e:cafe::24) by BY1P220CA0045.outlook.office365.com (2603:10b6:a03:59e::14) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.9846.28 via Frontend Transport; Tue, 28 Apr 2026 16:17:22 +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=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by CO1PEPF00012E7E.mail.protection.outlook.com (10.167.249.53) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9846.18 via Frontend Transport; Tue, 28 Apr 2026 16:17:21 +0000 Received: from Satlexmb09.amd.com (10.181.42.218) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 28 Apr 2026 11:17:21 -0500 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb09.amd.com (10.181.42.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 28 Apr 2026 09:17:20 -0700 Received: from [172.31.184.125] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Tue, 28 Apr 2026 11:17:17 -0500 Message-ID: <57e94d7e-b8fb-49bc-a914-8a7401e43af3@amd.com> Date: Tue, 28 Apr 2026 21:47:11 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND] sched/fair: Fix overflow in vruntime_eligible() To: Zhan Xusheng , Peter Zijlstra , Ingo Molnar , Vincent Guittot , Juri Lelli CC: , Zhan Xusheng , Dietmar Eggemann , Valentin Schneider , Ben Segall , Steven Rostedt , Mel Gorman References: <20260415145742.10359-1-zhanxusheng@xiaomi.com> <20260428144951.121765-1-zhanxusheng@xiaomi.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20260428144951.121765-1-zhanxusheng@xiaomi.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF00012E7E:EE_|MW4PR12MB7191:EE_ X-MS-Office365-Filtering-Correlation-Id: e0a0569f-3c9e-4d2e-90f5-08dea541a0b2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|82310400026|1800799024|36860700016|56012099003|18002099003|22082099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(7416014)(376014)(82310400026)(1800799024)(36860700016)(56012099003)(18002099003)(22082099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: bVF1XLfQ3zfFz/syOciaVJ4AabmgfiftffdYxSD5WYd6evFdtVIlQECGuI2kFREQzvgpq50ZnCqmWcUUdvVFrozSPP+IE0yUiEnbNV89MWbTgCQNnKI382r8fchQ12kCqvA9MFJmvNLoRlrFTyAmeCzDGTs6VuJVgeLB9DhKuscHe3slYpYz3Zwn6p0TpjhP0yDvwU41p+RpBZUfHK5NLRGERWJZwAy9FStCCGAwKahRrS1LiYcB5sYKsN5UpgnFGHS1BurcdgIIjwm5746ksWg0g8vRVc/aoxZ8MhVTtq/WSOTQQWKK+yFdVgsCpe6tiTuEoq+4ZBeo0IyiBGxfSO2X6eNM4oMJa0Ws38Mk33qYxVco6RmhUSYBpHfjvEQ5N3pz2+f2iw1R2ZHqSIx6WUVASr6rvx+FhY1depJxXnfTLUNLkB0V+PpmszjrTLkE X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Apr 2026 16:17:21.9314 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e0a0569f-3c9e-4d2e-90f5-08dea541a0b2 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF00012E7E.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB7191 (+ scheduler folks) Hello Zhan, On 4/28/2026 8:19 PM, Zhan Xusheng wrote: > After commit 556146ce5e94 ("sched/fair: Avoid overflow in > enqueue_entity()"), place_entity() can shift cfs_rq->zero_vruntime > towards a newly enqueued heavy entity. This can make (vruntime - > zero_vruntime) very large for other entities and cause key * load in > vruntime_eligible() to overflow s64, flipping the eligibility result. So the commit in question moves the zero_vruntime only when the load > sum_weight. You seem to have found a case where the entity_key() is already large enough that moving the zero_vruntime farther will make the eligibility check overflow which we were hoping will not be the case. Do you have a reproducer that fails pick_eevdf() after introduction of commit 556146ce5e94? Also, do you see any splats in the dmesg since we have a defensive WARN_ON() to catch an overflow. > > Use check_mul_overflow() for the multiplication and fall back to a > sign-based result on overflow. Don't we have PARANOID_AVG for that? Can you do: echo PARANOID_AVG > /sys/kernel/debug/sched/features # run your workload grep "sum_shift" /sys/kernel/debug/sched/debug and check if the "sum_shift" turns non-zero. > > Fixes: 556146ce5e94 ("sched/fair: Avoid overflow in enqueue_entity()") So we avoid a warning with that optimization but didn't see a crash anywhere without it during my testing. If you have a workload that crashes from those changes, perhaps we can see if there is a cheap enough way to move the zero_vruntime closer to the true average. -- Thanks and Regards, Prateek