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Wed, 1 Jul 2026 16:41:46 +0000 (GMT) Message-ID: <065ab092-a3ca-40b8-b335-a6568b9722a6@linux.ibm.com> Date: Wed, 1 Jul 2026 22:11:45 +0530 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 06/23] sched/fair: Load balance only among preferred CPUs To: Yury Norov Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, kprateek.nayak@amd.com, iii@linux.ibm.com, corbet@lwn.net, 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 References: <20260701141654.500125-1-sshegde@linux.ibm.com> <20260701141654.500125-7-sshegde@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=RYqgzVtv c=1 sm=1 tr=0 ts=6a45435d cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=EKe7ZLQl2c3Sbcnk6XUA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzAxMDE3MyBTYWx0ZWRfXzyE/H0RdiWim 0+YY1jKMsFIkQ5qCDrso1lSdLFIFz2dlS1bH4iihrvWEpf5RbmkyXN0Ev0e5ZyLy81ZECIMyevJ 05guXPVL+gFYybIGT4P5hUE5v2qWHZM= X-Proofpoint-GUID: aFRNraO90OH-ETita6ciPPczY2a3zFJ2 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzAxMDE3MyBTYWx0ZWRfXxoOXjpiycIyo 0g3N2Cto7n0qeq7D7zp1LpukZbEiNBQzLPznnEX6R2FvSyn2Tzpf006W5gFqAKVzX74dDbyJPox NVsoYGS7Oa3J4flda/uhxC3aEOo9cmhpHgz6sfDZAWJpV94kZVUvjihNBTAvv+yO0oTfPiXSb8s Oa8LSGT9ibhith155FHjeKmQVOA7pT5mVJKCP52ETWBT9lv61TWhauP1VmP18y0dFYSwCsfHwra kbQWGdNASXOPJtXjKLB0l76Tm22jLAE4f01vm6gTD3sxNqfq2vWOuds5EVaUSTKiZvcZP6qfuOa nM22LzESc9/Qv5Ofxpmx0pCFcviBnRYh81skHwtTWj//8D5GPhsVgLVr8ANPOb/GpOkqLfq93lH SJWC6GbuoIIUWAtjZ+Nb+FPlEVeCetnhhViyzsDg+uXXUVAUbpfMUC5IByfeqa619wVDTqGRsgA cgkR6DkR0j2ikWz2/Sg== X-Proofpoint-ORIG-GUID: UuxSCPqT855JJyaGmG22wXLz_llXJs4f 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 phishscore=0 impostorscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 adultscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607010173 On 7/1/26 9:49 PM, Yury Norov wrote: > On Wed, Jul 01, 2026 at 07:46:37PM +0530, Shrikanth Hegde wrote: >> 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 */ > > We don't have a "Spread load among active CPUs" comment. Don't think > it's more difficult to understand what happens if you replace one mask > with another. > Alright, I will drop it. >> + cpumask_and(cpus, sched_domain_span(sd), cpu_preferred_mask); >> >> schedstat_inc(sd->lb_count[idle]); >> >> -- >> 2.47.3