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Thu, 14 May 2026 15:24:00 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.124.213.185]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 14 May 2026 15:24:00 +0000 (GMT) From: Shrikanth Hegde To: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.com, kprateek.nayak@amd.com, iii@linux.ibm.com Cc: sshegde@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 Subject: [PATCH v3 08/20] sched/fair: load balance only among preferred CPUs Date: Thu, 14 May 2026 20:51:52 +0530 Message-ID: <20260514152204.481115-9-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260514152204.481115-1-sshegde@linux.ibm.com> References: <20260514152204.481115-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=KbvidwYD c=1 sm=1 tr=0 ts=6a05e91c cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=5ICBfrR2l7P1yX5hQRsA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTE0MDE1MyBTYWx0ZWRfX1E3julhN+G+M t5Ji/WnRsOXiUQLKpUIrennRXo+9L/PIAyaHrFaLX3JHCY0NFfZVIz79WcWlE4HTGFTgk7AuYDR KFrvQdeFX3lP9DWBMHiJgBsMLFXNRsQeVMkpNY9N1lM6YOitn8BAnej7ycn30FCZV3MLq0dyY2N gPRU7fuGV35QBTInqUTcAi4YZO9SP11mjhpBuHwKAn3k6CymEYicVPCAoaY6VIfTJOSMZDBC4u8 4JzxjTr8pk96KBXWP4qzGqiUeun24RdyQ5IxmEG4mEcJymHoUDLxu8Mpnb5WkkTgMWcgDEdcOlo d/06jXomoenGPOYogTitOpxMWNG4C8Oc+9XezhVQyIbRA3VX1+W5+bMGYinQ365wo8mxtj5cRos OY6z4eZvevJMjq5bVk5JYHAuBsYglrv104mijVIK8rRvFB0pxilmXdoeijSknvwwGQq75kGdGcq 5GowkMZw4PCx5ifq+nQ== X-Proofpoint-GUID: ebDrOF06tegTG3nOYh5debUsqXfoMkvP X-Proofpoint-ORIG-GUID: _rOFioNK5S3k0QEsJsU3c2vZVL8DxQpP 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=2026-05-14_03,2026-05-13_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 phishscore=0 spamscore=0 suspectscore=0 clxscore=1015 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605050000 definitions=main-2605140153 Consider only preferred CPUs for load balance. With this, load balance will end up choosing a preferred CPUs for pull. This makes it not fight against the push task mechanism which happens at tick. Also, this stops active balance to happen on non-preferred CPU pulling the load. This means there is no load balancing if the task is pinned only to non-preferred CPUs. They will continue to run where they were previously running before the CPUs was marked as non-preferred. Signed-off-by: Shrikanth Hegde --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a704285ac55a..0a851d4b0d7e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12087,6 +12087,9 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); + /* Spread load among preferred CPUs */ + cpumask_and(cpus, cpus, cpu_preferred_mask); + schedstat_inc(sd->lb_count[idle]); redo: -- 2.47.3