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Tue, 9 Jun 2026 04:42:28 +0000 (GMT) Message-ID: Date: Tue, 9 Jun 2026 10:12:27 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 07/20] sched/fair: Select preferred CPU at wakeup when possible To: Ilya Leoshkevich , K Prateek Nayak , linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.com Cc: 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 References: <20260514152204.481115-1-sshegde@linux.ibm.com> <20260514152204.481115-8-sshegde@linux.ibm.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: 09Iu4EVsho1mt5BKzviLZ7LnlG8pZdVX X-Proofpoint-GUID: 88h2TKEiinJhEj6sMtGlrEQzmx9f9BZx X-Authority-Analysis: v=2.4 cv=ZbEt8MVA c=1 sm=1 tr=0 ts=6a2799c1 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=aczH2RK3PXchF8pKeoAA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=O8hF6Hzn-FEA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA5MDAzOSBTYWx0ZWRfXxr0hQ0jL+P7c L/BnmICr3CP+uUp3NW/XYP0vJPlaqQzyLDhC99yfz82GFWR+udS8UJHQBJh465CY9sYYwTx66Du mXv+Lt7mywtauRXeJCVr8jpYIstaPcxX4f1SZgGxAiK9mNxgpSxHApl/BMhZyShxbJGj4EsUB8b rk6bTwdOgJ3pbUfL4xJq4C0cFTCVa+gP0z6WqfgXmgligvPa/AuCUcxcs5gnnwuWzCiJ0MQDwNs LvRtOr6dR3CBhIccJGjm5PvhFmeBVsf3LaWxsYELXcNbYRCTb8xOzTjOfKHpKhrRfjI4eJbnBqF lbx51jz3AOcXTdV8w+GBxJg6L6spJFx5NbfWS58ujKlMtAs9PSRu6OxVQI0cyquZrFoAbBzFoPH sfWrIO2vZr91Ouj+C47zqFpReu8ogO1xip0AGO4VeAvWDoSzK03SFXNu22d39NGofR4g2fLg+TK wS8vwzwYB5vm8hqp+vQ== 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=2026-06-09_01,2026-06-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 spamscore=0 priorityscore=1501 bulkscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606090039 Hi Ilya, Thank you very much for reviewing the patch series. On 6/8/26 10:09 PM, Ilya Leoshkevich wrote: > > > On 6/4/26 07:14, K Prateek Nayak wrote: >> Hello Shrikanth, >> >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index 29fbb5287cfc..a704285ac55a 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -7743,7 +7743,8 @@ static inline int >>> sched_balance_find_dst_cpu(struct sched_domain *sd, struct tas >>>   { >>>       int new_cpu = cpu; >>> -    if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr)) >>> +    if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr) && >> >> Doesn't this mean we have no CPUs in this sd that fits the affinity >> requirements? >> >>> +        cpu_preferred(prev_cpu)) >> >> There is no point in going down the function if the affinity constraints >> aren't met since we are traversing the hierarchy top-down and none of >> the groups / child domains will satisfy the affinity requirements. >> >> Since the CPU returned here is again checked for is_cpu_allowed(), we'll >> eventually hit the select_fallback_rq() path anyways so the check for >> cpu_preferred(prev_cpu) seems unnecessary unless I'm missing something. > > Do we need to add is_cpu_allowed() check to sched_exec()? > Or is the existing cpu_active() check enough? > sched_exec select_task_rq if (!is_cpu_allowed() select_fallback_rq That is going to select based on preferred state and its affinity mask. So, i think we are good there.