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Sun, 11 Oct 2026 21:29:46 -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 15.2.2562.53; Sun, 11 Oct 2026 21:29:46 -0500 Received: from [10.136.45.168] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.53 via Frontend Transport; Sun, 11 Oct 2026 21:29:38 -0500 Message-ID: <801adad4-fbcb-45f8-9283-c35676cd4d63@amd.com> Date: Mon, 12 Oct 2026 07:59:36 +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: [RFC PATCH v3 06/13] powerpc/setup: Initialize sbm topology based on coregroup / NUMA topology To: Shrikanth Hegde , Peter Zijlstra , Michael Ellerman , , Madhavan Srinivasan , Thomas Gleixner CC: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Nicholas Piggin , Christophe Leroy , Chen Yu , Tim Chen , Ingo Molnar , Juri Lelli , Vincent Guittot , Andrew Morton , "Arnd Bergmann" , , , , , , , Ritesh Harjani , "Srikar Dronamraju" References: <20261001192849.74788-1-kprateek.nayak@amd.com> <20261001192849.74788-7-kprateek.nayak@amd.com> <61b01870-ddcf-4c4f-8604-dd63aa4a07a3@linux.ibm.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <61b01870-ddcf-4c4f-8604-dd63aa4a07a3@linux.ibm.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: kf9AiQhl//3lnaN1h0NHHjRINv+s4GJq027bktm1OCnUJFtoH9M4pPTxnsAVnJP4hCMqvPL6VvQ065EPS2skTwcGlS0hRbaxMHeesyCcNAOgh5YOrS4+sI0LNIOhs/QX0UjziLmnN3X9lmUuYIN43gfRsdXf0ONoZKSLPH7pYuohrHC+Y9GTyS7V+hKrR6IqE003lhvXwmMGo6gptJsRDb7FiJsi4U3s8RKIPPw7+mRcLCrcV/naolvM0PDDsdI/1C0vNXJByl1rNyor5PZNwlseCQWSkBOZW+X95bXO1HYvl0qBk8ZwZW/hke0Snbs7vPvyTZMsED47/0RmUvQ1fJ5uMNgF8dtByDcamE0g1N+6db6B14z8grLaJLHV33cnm4+1WJMtOcaMlszTFynAoSQ+D+Pchjwq5OY4eJICd372IDrXfNvswKA2LeTOnGc8 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Oct 2026 02:29:52.5073 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 23a9f0a2-b7c1-4c8b-0673-08df2808b245 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: CH2PEPF00000141.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB6173 Hello Shrikanth, On 10/7/2026 8:13 PM, Shrikanth Hegde wrote: > Hi Prateek. > > On 10/2/26 12:58 AM, K Prateek Nayak wrote: >> Initialize sparsebitmap (sbm) topology based on the coregroup >> information. Each coregorup gets its own sparsemask leaf. >> >> pSeries and memory hotplug are interesting since a hotplug can place a >> newly added CPU on any online node. This requires special care to allow >> estimating bitmask size considering the worst case scenarios - each CPU >> onlined is on a separate node, and this is a new N_CPU node. >> >> Platform may enforce a stricter standards for the CPUs being online and >> what nodes they can be mapped to but the current implementations makes >> no assumptions and considers each CPU can be onlined on a unique node. >> > > I think this suffers the same fate as structures which are allocated at boot > time such as runqueues. > > So your fallback option of putting all the disabled into singleton node may be > sensible option. (If you are not doing that already) For pSeries I allocate a humongous chunk of memory on sbm_alloc() and control how much of that memory needs traversing based on the set of online CPUs. Not ideal but yes, I will probably pivot to doing something like what per-cpu setup does by using ealy topology + assuming a few things about the rest. > But yhea, will see more into it, this changing node stuff is new for me too. > Also i need to read your patch series too :) Thank you again for taking a look at the series and early testing. _Me goes digs down on couple regressions I've noticed_ -- Thanks and Regards, Prateek