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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by MWH0EPF000971E8.mail.protection.outlook.com (10.167.243.68) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9564.3 via Frontend Transport; Fri, 23 Jan 2026 12:24:41 +0000 Received: from satlexmb10.amd.com (10.181.42.219) 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; Fri, 23 Jan 2026 06:24:40 -0600 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb10.amd.com (10.181.42.219) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Fri, 23 Jan 2026 06:24:40 -0600 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; Fri, 23 Jan 2026 04:24:36 -0800 Message-ID: <52b5b07d-89ee-4266-a229-ce9a8c6f8cb1@amd.com> Date: Fri, 23 Jan 2026 17:54:30 +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 4/4] sched/fair: Proportional newidle balance To: Peter Zijlstra , Mario Roy CC: Chris Mason , Joseph Salisbury , Adam Li , "Hazem Mohamed Abuelfotoh" , Josh Don , , , , , , , , , References: <20251107160645.929564468@infradead.org> <20251107161739.770122091@infradead.org> <8760001e-0274-454c-a4e4-1f38a9695b88@gmail.com> <20260123105046.GM171111@noisy.programming.kicks-ass.net> <20260123110306.GA217302@noisy.programming.kicks-ass.net> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20260123110306.GA217302@noisy.programming.kicks-ass.net> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jan 2026 12:24:41.2216 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6a0ff1d0-c0b9-476d-6d7c-08de5a7a6238 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: MWH0EPF000971E8.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW6PR12MB8758 Hello Peter, On 1/23/2026 4:33 PM, Peter Zijlstra wrote: > On Fri, Jan 23, 2026 at 11:50:46AM +0100, Peter Zijlstra wrote: >> On Sun, Jan 18, 2026 at 03:46:22PM -0500, Mario Roy wrote: >>> The patch "Proportional newidle balance" introduced a regression >>> with Linux 6.12.65 and 6.18.5. There is noticeable regression with >>> easyWave testing. [1] >>> >>> The CPU is AMD Threadripper 9960X CPU (24/48). I followed the source >>> to install easyWave [2]. That is fetching the two tar.gz archives. >> >> What is the actual configuration of that chip? Is it like 3*8 or 4*6 >> (CCX wise). A quick google couldn't find me the answer :/ > > Obviously I found it right after sending this. It's a 4x6 config. > Meaning it needs newidle to balance between those 4 domains. > > Pratheek -- are you guys still considering that SIS_NODE thing? That > worked really well for workstation chips, but there were some issues on > Epyc or so. SIS_NODE was really turned out to be a trade-off between search time vs search opportunity, especially when the system was heavily overloaded. Let me rebase those old patches and give it a spin over the weekend on a couple of those large machines (128C/256T and 192C/384T per socket) to see the damage. I'll update here by Tuesday or post out a series if I see the situation having changed on the recent kernels - some benchmarks had a completely different bottleneck there when we looked closer last. > >>> #!/bin/bash >>> # CXXFLAGS="-O3 $CXXFLAGS" ./configure >>> # make -j8 >>> >>> trap 'rm -f *.ssh *.idx *.log *.sshmax *.time' EXIT >>> >>> OMP_NUM_THREADS=48 ./src/easywave \ >>>   -grid examples/e2Asean.grd -source examples/BengkuluSept2007.flt \ >>>   -time 1200 >>> >>> >>> Before results with CachyOS 6.12.63-2 and 6.18.3-2 kernels. I'll go look at the benchmark too to see if I can reproduce on my end and get some stats for these too. Thanks for bringing it to my notice. -- Thanks and Regards, Prateek