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Wed, 19 Nov 2025 06:21:52 +0000 (GMT) From: Shrikanth Hegde To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: sshegde@linux.ibm.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, tglx@linutronix.de, yury.norov@gmail.com, maddy@linux.ibm.com, srikar@linux.ibm.com, gregkh@linuxfoundation.org, 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, christophe.leroy@csgroup.eu Subject: [RFC PATCH v4 06/17] sched/fair: Pass current cpu in select_idle_sibling Date: Wed, 19 Nov 2025 11:50:49 +0530 Message-ID: <20251119062100.1112520-7-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251119062100.1112520-1-sshegde@linux.ibm.com> References: <20251119062100.1112520-1-sshegde@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: PrOkUxaqOlOHFsjN3g62TBwDejMTEiDX X-Proofpoint-ORIG-GUID: DTGLePjwWXwpfo3xylAp3_fkws5dHnxw X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX98HpljThVV0W EqT6vhVl8DEoLO9LVbkP25gY9L0EtroIoPa4JhocW23DzOqBEz1lxB6YfEZ+474SCnbhyaKfBh/ BPPUn+upsqReJpYNFj9l3jJC0KJMKd5u3N/tBvYtdsANcJi3kDsqMMHg/PMYQTsqiPrVGF3RC7n QRWvRKdT6XeQyqGJ9yo+0mgJSVnpyrZXXxnLcwF/IReAbmEd5g4ouqAB2UthNScVZzY+O5nHjzj ZhTjpBbGExjW/6aAUg7GENHVdNNGUn9IFjI4MDEZATqXD/GWolS5Kkk2D4TW260U63FsBMe2Whl X3GY9R6i8xLlAIIiMG8Y+4l2xv1pgCujFcap6a9wYQofiAoEaTD+lm5djoPfwY8xXlFW8HhdKOq blqq2ssCOGKG+QaDYGjIcXj68ob1FQ== X-Authority-Analysis: v=2.4 cv=SvOdKfO0 c=1 sm=1 tr=0 ts=691d6209 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=LR1EqIGjcEKtFJDgD-kA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-19_01,2025-11-18_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 spamscore=0 clxscore=1015 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 impostorscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 Pattern in select_task_rq_fair: cpu = smp_processor_id(); new_cpu = prev_cpu; //May change new_cpu due to wake_affine, otherwise it remains prev_cpu new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); Due to this often prev_cpu == new_cpu. If the task was sleeping when the prev_cpu was marked as paravirt, it would be beneficial to choose current cpu instead. If the current cpu is paravirt too, then wakeup will happen there and at next tick task will move out. So pass current CPU as well in the select_idle_sibling. Signed-off-by: Shrikanth Hegde --- kernel/sched/fair.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1855975b8248..015e00b370c9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1048,7 +1048,7 @@ static bool update_deadline(struct cfs_rq *cfs_rq, struct sched_entity *se) #include "pelt.h" -static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu); +static int select_idle_sibling(struct task_struct *p, int this_cpu, int prev, int target); static unsigned long task_h_load(struct task_struct *p); static unsigned long capacity_of(int cpu); @@ -7770,7 +7770,7 @@ static inline bool asym_fits_cpu(unsigned long util, /* * Try and locate an idle core/thread in the LLC cache domain. */ -static int select_idle_sibling(struct task_struct *p, int prev, int target) +static int select_idle_sibling(struct task_struct *p, int this_cpu, int prev, int target) { bool has_idle_core = false; struct sched_domain *sd; @@ -8578,7 +8578,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) new_cpu = sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag); } else if (wake_flags & WF_TTWU) { /* XXX always ? */ /* Fast path */ - new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); + new_cpu = select_idle_sibling(p, cpu, prev_cpu, new_cpu); } rcu_read_unlock(); -- 2.47.3