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Thu, 18 Jun 2026 04:42:19 +0000 (GMT) Received: from [9.123.5.233] (unknown [9.123.5.233]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 18 Jun 2026 04:42:19 +0000 (GMT) Message-ID: Date: Thu, 18 Jun 2026 10:12:18 +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 v4 16/20] sched/core: Introduce default arch handling code for inc/dec preferred CPUs To: Yury Norov Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, kprateek.nayak@amd.com, iii@linux.ibm.com, tglx@kernel.org, gregkh@linuxfoundation.org, pbonzini@redhat.com, seanjc@google.com, vschneid@redhat.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, mgorman@suse.de, bsegall@google.com, maddy@linux.ibm.com, srikar@linux.ibm.com, hdanton@sina.com, chleroy@kernel.org, vineeth@bitbyteword.org, frederic@kernel.org, arighi@nvidia.com, pauld@redhat.com, christian.loehle@arm.com, tj@kernel.org, tommaso.cucinotta@gmail.com, maz@kernel.org, rafael@kernel.org References: <20260617174139.155540-1-sshegde@linux.ibm.com> <20260617174139.155540-17-sshegde@linux.ibm.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-Spam-Details-Enc: AW1haW4tMjYwNjE4MDAzNSBTYWx0ZWRfX711icKCgzCL5 P2/aNyjXLZJwxrLNVf8oddZEseFJ/xlODZH9fYUzoTnFTEawB7W/6aZVrUi+Lhhhtl6kNiOqs5j Qu+GIZVFqBJD2DDiR6cqn3A3E9whT7/GsJLRdxDJGB82X2euRxlhlx6qAs6f8omnoeWKvVK/sxM HR583kJXM2Z5uFZG1FCHBRxQs94lF3aiAL15GZcUfANJsJhtCNKmHWYseIYCReG41al31WyhJ/r DIlVqohWbd133IXcNNU1QRccSSJ2EaUfcL9641+5LlMQ6ZtKPvEJ1XZCxhRxh8X9ihQF7Pxzauh c/U4mmARgWZKsNMwFcxyYjXZ+BDKcwJPB87o99ARb9xsm52O/+ZrjzHUwg0+yXRbf0inukg0jCp aC+zD3ZkgPTKRgv9fK7C1yRKKeylD+1x1zohtU7zblWM+bHU7g+Uvjt6Irom0JyhBmtIGpU7Mxt noyVqgyQ1CYeYTRaRLg== X-Proofpoint-GUID: AbnagiKZxd5RJOCIlXCqK4C8PGMjwcVj X-Proofpoint-Spam-Info: AW1haW4tMjYwNjE4MDAzNSBTYWx0ZWRfX9sikXUQJJYAh gtSNXLailzko2Dh2CMZZLSWyc5JDzkgeYIJ+4aS/TOyYf5bSwfxnITT+vfSz3C8LvsHKzd1BOS1 fu2Xmpn7em2v0PmFVpaQ8Btfaism/Fo= X-Proofpoint-ORIG-GUID: 2ERz0tbH7oD76E3skh4rw6p9gh3QshjK X-Authority-Analysis: v=2.4 cv=auGCzyZV c=1 sm=1 tr=0 ts=6a337738 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=ASg7Ikj4zqaxa_AaHEkA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-17_02,2026-06-17_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 adultscore=0 malwarescore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606180035 On 6/18/26 9:45 AM, Yury Norov wrote: > On Wed, Jun 17, 2026 at 11:11:35PM +0530, Shrikanth Hegde wrote: >> Define default handlers for high/low steal time. If arch has better >> decision logic, may override the default implementation. >> >> - If the steal time higher than threshold, reduce the number of preferred >> CPUs by 1 core. The last core in the intersection of active and >> preferred CPUs will be marked as non-preferred. >> Ensure at least one core is left as preferred always. >> >> - If the steal time lower than threshold, increase the number of preferred >> CPUs by 1 core. First active core which is not in cpu_preferred_mask will >> be marked as preferred. >> If all cores are already set to preferred, bail out. > > And the code below does nothing of that. Agree. My bad. This changelog needs update. > >> Increase/Decrease may need to modify the splicing across NUMA nodes. It is >> being kept simple for now. >> >> Signed-off-by: Shrikanth Hegde