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Thu, 25 Jun 2026 12:48:03 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.39.20.6]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 25 Jun 2026 12:48:03 +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 v5 08/24] sched/fair: load balance only among preferred CPUs Date: Thu, 25 Jun 2026 18:16:32 +0530 Message-ID: <20260625124648.802832-9-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260625124648.802832-1-sshegde@linux.ibm.com> References: <20260625124648.802832-1-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-Authority-Analysis: v=2.4 cv=X4Ni7mTe c=1 sm=1 tr=0 ts=6a3d2391 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=5ICBfrR2l7P1yX5hQRsA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjI1MDExMCBTYWx0ZWRfXwGpN604sncuc 7ghlMeH6e3gSBbFiA7VGCxxRcegLkONEJ58TMiCdB4xyw8BAI20u4wad3oFtueao3IayXq7Jxs6 wUz0Y4cZ42Nt8xHV0ZktzKtJX9Yo4Qw= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjI1MDExMCBTYWx0ZWRfX895vlcDJ9PKG G613+FS3u/7AlaqSGSG701Mk4K6JAXk0yeNQya26LLTrIvgLumkkKH9X3u7ujSEnVia2UJ6mSh2 eUw9iXep7adjjkyTrs94n5+F81/wYyGdZeeLU63E6xctjGYUOg84Sw7Aohon6fYLs+g1MsNYahC XEW+TBcu8QzkcBTdXvdY5xtyrCJGDXPFV5OOkao+/nDiQMPJfkGGKH3L2Wb5efErjcv5nVWO7MH M8AKUKAyhnSLn0V94jXC4QVorb9lFRU9I5tHJxlkpvhTBWgtG7keWU5NV0ZWzgXS+wxuIRxh2GY dNEHkt+F498hRxvMtjJr+YMCuwWqGgCcR+lZgd9JNqzB7TowFqx79DaX+aWKYymzpnfjcKAz6f4 NBKDZrlf1fduTNYmEE35sjxX0aZ1A6xZVoSzz7+8ZVdoKxNQ+UaeUMI8JiT+sK6hM1+gRPZrV5N m5Y99J+cC2axofRFusw== X-Proofpoint-ORIG-GUID: QyWcO4AWMQV3mMgZIicumcBp-Sz6eLNi X-Proofpoint-GUID: iaQXZf-nY5cKjg1SDKufp2ANa00OkZuz 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=2026-06-25_01,2026-06-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 suspectscore=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606250110 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 --- v4->v5: - Remove previous cpumask_and (K Prateek Nayak) 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 d78467ec6ee1..44a0d9736b67 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -13289,7 +13289,8 @@ 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