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Sat, 28 Mar 2026 06:51:30 +0000 (GMT) Message-ID: Date: Sat, 28 Mar 2026 12:21:19 +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 0/4] sched/fair: SMT-aware asymmetric CPU capacity To: Andrea Righi Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Loehle , Koba Ko , Felix Abecassis , Balbir Singh , linux-kernel@vger.kernel.org References: <20260326151211.1862600-1-arighi@nvidia.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: zv8Z6NJlAf28adXVDBJxXMRatSqF2fUJ X-Authority-Analysis: v=2.4 cv=KslAGGWN c=1 sm=1 tr=0 ts=69c77a79 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=_2WsoeLZRHrrawEVrbUA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI4MDA0NyBTYWx0ZWRfXzuf8hKIKpZ7E P73T9CmFoxhdj24PSLzr3KW0FnWWYoKBUmfhzmjl7PaQ+E7wUPRtT3Dz85YQdVZu7dQ9E4Mnqei bhWJHqvFZuyWiFcq5ikBznhoHloDl5TgX3zHMWWsnQSItaf9g9rfNrkGqY7hCgeYBbARdn5qJwO 09W9lA12HRoMWU4/oDFcQcm4K+itj5UuxNxf/JAixeF0V9LrxERhvK6lL/fInftvyTdH0G9WQLI pPqyKN0ReegrMuWO1UKNcbx6BXt2YWDIy+Rj45525Gf6vPNCPBfRaweIJSTs8UO+dPDey5v7IXe bvr84avVJ8NQCk+Jjx+tekrZXnN5eudbguGrI+2IYjiZAFW+EFnRLFsCvoPG1QpA3efPLnELSWP wWRdQhHC8Ar9bzpmv/GsDp0QZhfBAFFSN1irW79U63QAVRrCtYnBP7d8PCdCdWlH0j5yU3HXa37 kfRzRzuPUC9KCspkoSg== X-Proofpoint-ORIG-GUID: 38c17ZfDhr-WSkwNHrHlVBl5vQRBwU4U X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-27_02,2026-03-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 impostorscore=0 clxscore=1015 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603280047 >> How is the performance measured here? Which benchmark? > > I've used an internal NVIDIA suite (based on NVBLAS), I also tried Linpack > and got similar results. I'm planning to repeat the tests using public > benchmarks and share the results as soon as I can. > >> By any chance you are running number_running_task <= (nr_cpus / smt_threads_per_core), >> so it is all fitting nicely? > > That's the case that gives me the optimal results. > >> >> If you increase those numbers, how does the performance numbers compare? > > I tried different number of tasks. The more I approach system saturation > the smaller the benefits are. When I completely saturate the system I don't > see any benefit with this changes, neither regressions, but I guess that's > expected. > Ok. That's good. I gave hackbench on powerpc with SMT=4, i didn't observe any regressions or improvements. Only PATCH 4/4 applies in this case as there is no asym_cpu_capacity