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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BN2PEPF00004FBF.mail.protection.outlook.com (10.167.243.185) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8699.20 via Frontend Transport; Wed, 30 Apr 2025 03:33:34 +0000 Received: from [10.85.37.104] (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, 29 Apr 2025 22:33:29 -0500 Message-ID: Date: Wed, 30 Apr 2025 09:03:26 +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: EEVDF regression still exists To: "Prundeanu, Cristian" , Peter Zijlstra CC: "Mohamed Abuelfotoh, Hazem" , "Saidi, Ali" , Benjamin Herrenschmidt , "Blake, Geoff" , "Csoma, Csaba" , "Doebel, Bjoern" , Gautham Shenoy , Swapnil Sapkal , Joseph Salisbury , Dietmar Eggemann , Ingo Molnar , Linus Torvalds , Borislav Petkov , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-tip-commits@vger.kernel.org" , "x86@kernel.org" References: <20250429213817.65651-1-cpru@amazon.com> <20250429215604.GE4439@noisy.programming.kicks-ass.net> <82DC7187-7CED-4285-85FC-7181688CD873@amazon.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <82DC7187-7CED-4285-85FC-7181688CD873@amazon.com> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Apr 2025 03:33:34.4221 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: cb1f224d-3af6-43af-b353-08dd8797c95d 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: BN2PEPF00004FBF.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYYPR12MB8701 Hello Cristian, On 4/30/2025 3:36 AM, Prundeanu, Cristian wrote: > On 2025-04-29, 16:57, "Peter Zijlstra" > wrote: > >>> Here are the latest results for the EEVDF impact on database workloads. >>> The regression introduced in kernel 6.6 still persists and doesn't look >>> like it is improving. >> >> Well, I was under the impression it had actually been solved :-( >> >> My understanding from the last round was that Prateek and co had it >> sorted -- with the caveat being that you had to stick SCHED_BATCH in at >> the right place in MySQL start scripts or somesuch. > > The statement in the previous thread [1] was that using SCHED_BATCH improves > performance over default. While that still holds true, it is also equally true > about using SCHED_BATCH on kernel 6.5. > > So, when we compare 6.5 with recent kernels, both using SCHED_BATCH, the > regression is still visible. (Previously, we only compared SCHED_BATCH with > 6.5 default, leading to the wrong conclusion that it's a fix). So I never tried comparing SCHED_BATCH on both old vs new kernel for the HammerDB benchmark since SCHED_BATCH had not led to a great improvement in the baseline numbers on v6.5 in my previous debugs and I was mostly looking at context-switch data, trying to match the EEVDF case to baseline numbers. I'll try to setup the reproducer you have posted on my end and reach out if I run into any issues. Hopefully the exact setup reveals something I've overlooked. P.S. Are the numbers for v6.15-rc4 + SCHED_BATCH comparable to v6.5 default? One more curious question: Does changing the base slice to a larger value (say 6ms) in conjunction with setting SCHED_BATCH on v6.15-rc4 affect the benchmark result in any way? > > [1] https://lore.kernel.org/all/feb31b6e-6457-454c-a4f3-ce8ad96bf8de@amd.com/ > -- Thanks and Regards, Prateek