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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=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by PH1PEPF00062F26.mail.protection.outlook.com (10.167.243.55) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.522.6 via Frontend Transport; Fri, 23 Oct 2026 03:23:02 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.53; Thu, 22 Oct 2026 22:23:02 -0500 Received: from [10.85.46.93] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.53 via Frontend Transport; Thu, 22 Oct 2026 22:22:59 -0500 Message-ID: <9d1381a4-6f4f-48aa-b76f-fad11e9d5bc9@amd.com> Date: Fri, 23 Oct 2026 08:52:58 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] sched/pelt: Fix truncation of the PELT period count To: Hui Su , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot CC: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Kayra Cizmeci , References: <20261023025207.2967903-1-sh_def@163.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20261023025207.2967903-1-sh_def@163.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: LZ+JpnA5o7IwFF2WORP7Tb61oJ4Qvx0xPhsfYvqV4h52Vb3nI69YsW2LBPnLHYx5zicafnyZ6OY9SLX9DyNh2dSRP1FZb1fN/uWMyiec52rN9uFgAc6xbrYG+qVCFiTnoo69izIBtvIV3RzfUVZxFfUBkMOff4Fiq+F/LMtmUkyx0N5CeWi9DOA4ADZaS/KJt8qLOKe2IHIohdL5I4d6iazerpj6tiNknyXkrx1zqjX/WnaPHevmmIf4UU2OgCGG+fIzS1yMHhU2u1sKeOiY+BwWt4CRfzRuJnJzH9ljV8GnUq8IpnPXjImhh3gI2CM7Odv/9QnIPGuupJjJLwnz6JudUb67sGEqGKo2pd2qNxS0wDCmaXxXnHsn7PZyzwu1887dhRTp9k7Gc1nh1VttZtrxFXrM6dr4Yq9PuCSd+zhFk/tqRv/4Yjn8WUCZSPTy X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Oct 2026 03:23:02.8021 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c3237247-1acb-4a50-dd7c-08df30b4f268 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: PH1PEPF00062F26.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW6PR12MB8898 Hello Hui, On 10/23/2026 8:22 AM, Hui Su wrote: > accumulate_sum() computes the number of elapsed PELT periods in a > u64 but returns u32. When the count is a multiple of 2^32, it is > truncated to zero even though the PELT sums have been updated. > > The caller interprets zero as no period boundary crossed and skips > recomputing the averages, leaving *_avg stale relative to *_sum. > > Return the period count as u64 so the caller can test it without > truncation. > > Fixes: a481db34b9be ("sched/fair: Optimize ___update_sched_avg()") > Reviewed-by: Vincent Guittot > Reviewed-by: Kayra Cizmeci > Signed-off-by: Hui Su Feel free to include: Reviewed-by: K Prateek Nayak > --- > Changes in v2: > - Return the PELT period count as u64. > - Add the Fixes tag and Kayra Cizmeci's Reviewed-by. > > v1: https://lore.kernel.org/lkml/20261022034930.225042-1-sh_def@163.com/ > > kernel/sched/pelt.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > index 779eb58a4261..d10d57b6b8ec 100644 > --- a/kernel/sched/pelt.c > +++ b/kernel/sched/pelt.c > @@ -99,7 +99,7 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) > * d1 y^p + 1024 \Sum y^n + d3 y^0 (Step 2) > * n=1 > */ > -static __always_inline u32 > +static __always_inline u64 > accumulate_sum(u64 delta, struct sched_avg *sa, > unsigned long load, unsigned long runnable, int running) > { > > base-commit: a804c5742bff224d4cb4d25dd383554d598be32b -- Thanks and Regards, Prateek