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Tue, 7 Apr 2026 19:20:41 +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, tglx@linutronix.de, yury.norov@gmail.com, gregkh@linuxfoundation.org Cc: sshegde@linux.ibm.com, pbonzini@redhat.com, seanjc@google.com, kprateek.nayak@amd.com, vschneid@redhat.com, iii@linux.ibm.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, joelagnelf@nvidia.com Subject: [PATCH v2 07/17] sched/fair: load balance only among preferred CPUs Date: Wed, 8 Apr 2026 00:49:40 +0530 Message-ID: <20260407191950.643549-8-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260407191950.643549-1-sshegde@linux.ibm.com> References: <20260407191950.643549-1-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-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDA3MDE3NSBTYWx0ZWRfXz1QUTVL0MTkj YD/Uw1bIDFjytFAgBNFq94SyT9BIsfTcW9ikowiAt4lAy8BNtOWRM/doBmpPI8GY+fcwSo6pfnL ZSzQXRa0B2GUtEouljH7JzETUaEjeHJs686M/hq7u2Wtdc3W6nKGbNzoEx/g0dFyZgqGvhYFD/u t2++k4XEoJbQO6NMcruh2LUxJRr+kGpp8S7Tx5zUqNJNLhYhx90r5Hm5dTKzyPmSaWF6IxK7Y8c hjT5DHw1++RToz51Uy3c5tyoKimO7DQDR+ElFclyY6rct+th+xuWGx+jgdbQfMij0bWR10CMQ+O xyy/6wy1Eu5lCGiZM/QlDziu/eTme1bXVt+4Bv9mOmlKz3L3V1NKt7egkmeeiPHXzU7wQEuJu89 O3/Rgmbbbgjst3Yx354zcVbhswQWSUqIQQBlbwUrfF+WMxqOXwyyEBmiaEKbdjzxWLzM3Z1Wh02 hYk6dJMyjfTnJ5MS4Vg== X-Proofpoint-ORIG-GUID: zKHRzHXyAU2JHRShKItazNvu49sZBRSE X-Authority-Analysis: v=2.4 cv=e9k2j6p/ c=1 sm=1 tr=0 ts=69d55914 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=5ICBfrR2l7P1yX5hQRsA:9 X-Proofpoint-GUID: OitUDIaExvde2pxCsrr88atG_ODrkZL6 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=2026-04-07_04,2026-04-07_05,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 malwarescore=0 suspectscore=0 spamscore=0 bulkscore=0 adultscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604070175 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 | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 22010afb4c1d..e4571bd71a44 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12058,6 +12058,11 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); +#ifdef CONFIG_PARAVIRT + /* Spread load among preferred CPUs */ + cpumask_and(cpus, cpus, cpu_preferred_mask); +#endif + schedstat_inc(sd->lb_count[idle]); redo: -- 2.47.3