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Tue, 9 Jun 2026 11:33:22 +0000 (GMT) Message-ID: Date: Tue, 9 Jun 2026 17:03:21 +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 v3 08/20] sched/fair: load balance only among preferred CPUs To: Peter Zijlstra Cc: K Prateek Nayak , linux-kernel@vger.kernel.org, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.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: <20260514152204.481115-1-sshegde@linux.ibm.com> <20260514152204.481115-9-sshegde@linux.ibm.com> <0aa0d84c-9d0e-4ca1-9a9c-6370976a0974@amd.com> <8281bd2a-31a1-4e18-aea2-830777a454a6@linux.ibm.com> <20260609112232.GB48970@noisy.programming.kicks-ass.net> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20260609112232.GB48970@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA5MDEwNCBTYWx0ZWRfXzOW/PjcDgAsi S7d2n+/ctzsQZ9ZNGzmJFODXNDIdPzx1jrlcusWjIIvUN2RDjnrjO2wmr4o69XnV0Ov9j0NmxPw vuFZRJcy9yGdsHn26ddPcMcQ9MrM2diWTEgW3uvQ6eH2HoSfW1JF3PhowTS5WSNf8v69TD1W3ho PXoSfrHzppWeM9x3z9tcEEEaaXlLbyacAHfD3E3+pY0RFpePM65MiJtJUimBCdd4Cfjrn4rjpJr WEyTo61VCzZJc3HfdBG75frbe8apD/XOho18A/W4dXdJvXztgwNmu5QIRHzmC63wv08kPYbPwEA qCzdBtEuYCMoMVrRytmhMBGf6Z+7FDk2PsXFT4T//EqOl8ZSHT7i+UeHVSrJrFvENatfuqzTCpY 78jI9aGtENkFVsgkCQuM+VbbrWt1NpDQA2JG7UOUm1Xq8n6OkBHaPAjBg7f7fMtxvpPuKSJh6qO ufzQnq3j5qQoLIGLDPA== X-Authority-Analysis: v=2.4 cv=QKhYgALL c=1 sm=1 tr=0 ts=6a27fa10 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=4cEMFjHkuC7lKcce3CsA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: W6AQEQYQYk4dKRwwxMDP9XxAPmDxA-5w X-Proofpoint-ORIG-GUID: KdivJjTLyiMc78u_ww1x0setjgOsHHxn 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=2026-06-09_02,2026-06-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 suspectscore=0 spamscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606090104 On 6/9/26 4:52 PM, Peter Zijlstra wrote: > On Thu, Jun 04, 2026 at 06:37:48PM +0530, Shrikanth Hegde wrote: >> Hi Prateek. >> >> On 6/4/26 11:39 AM, K Prateek Nayak wrote: >>> Hello Shrikanth, >>> >>> ... just moving set_cpu_preferred() into sched_cpu_activate() and >>> sched_cpu_deactivate() instead of doing it at set_cpu_online(). >>> >> >> Ah ok. Will move it there. I think this should be ok. > > Right, such that preferred is a strict subset of active. > > preferred ⊆ active ⊆ online ⊆ present ⊆ possible Ok. This can be met i think. In addition to this and in the dec/incr of preferred CPUs if i plug active mask instead of online, and disable make it same as active the above construct can be met i think. I will give that a try. That might make it better w.r.t to CPU hotplug too. less races.