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Wed, 1 Jul 2026 14:18:24 +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, corbet@lwn.net 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, 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, rdunlap@infradead.org, kernellwp@gmail.com, linux-doc@vger.kernel.org Subject: [PATCH v6 06/23] sched/fair: Load balance only among preferred CPUs Date: Wed, 1 Jul 2026 19:46:37 +0530 Message-ID: <20260701141654.500125-7-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260701141654.500125-1-sshegde@linux.ibm.com> References: <20260701141654.500125-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-doc@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-Proofpoint-GUID: Q_wBDq13sEbeR9TRfbHNfzjtPc9PlIvZ X-Proofpoint-Spam-Info: AW1haW4tMjYwNzAxMDE1MCBTYWx0ZWRfX0dSzlZTmHaMU Ib+6Fs86r+R6z8WDaI5HcVbq+hk6U8CJ8onPqZh5O60l0SlM7src6RBYTlPv7c4IZEkjjnKQC7H FJBGq7s4JQhbN/i+FYyNmRNU5UahjBs= X-Authority-Analysis: v=2.4 cv=edsNubEH c=1 sm=1 tr=0 ts=6a4521c4 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=5ICBfrR2l7P1yX5hQRsA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzAxMDE1MCBTYWx0ZWRfX22AYtszHWYVi ZCifvINGEE148qg4j7bbJRiYs9jLf3mnzEnwNVHQcvO4IeBKe4QXD4QSwyPsTCvPtGrDqTLz0hB kdW1IGKAkzjR0p4wIPZWF/AMqisQoE4hV4PDUr4SMeYM5ZYpkZFZk+/eglSi7df2eRrpWN9XUv4 wID/awMZJjH1wNOLLo5/1v7pnKAmg49Vjom+mMO5pQyypwzG71JT5wHVGoMQgTT0oVTYvmiYavC 1SCouqecb8cEVbHsbWOrF2/X+hL4PQHzH1agDbDEZuZZTXk//kChgyAEdE33Wj1HZdoMBArCdMO WDUetgDKHZ9si4F0hbHZmfgP/x12GL8sAdEEQ/Ez24VWfDfCIyPEtTTFvwAJqWV8AlkjHAimUJ0 GGYuqWlqjHcUF3oGwTboeStw2lSb6jK68EIZrJ8oJ1Q++P2HbJHfc9vm3qvOQkN3IYP6x/tNPNO ScVEnnrYT34X5iDZ30Q== X-Proofpoint-ORIG-GUID: 163oTwniMVyMkM8qD1NYSlos8OqDfngN 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=2026-07-01_03,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 adultscore=0 impostorscore=0 bulkscore=0 spamscore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607010150 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, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ce05acf52d35..9b2931b559d6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -13391,7 +13391,8 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, }; bool need_unlock = false; - cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); + /* Spread load among preferred CPUs */ + cpumask_and(cpus, sched_domain_span(sd), cpu_preferred_mask); schedstat_inc(sd->lb_count[idle]); -- 2.47.3