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Wed, 25 Jun 2025 19:11:48 +0000 (GMT) From: Shrikanth Hegde To: 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 Cc: sshegde@linux.ibm.com, vschneid@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, kprateek.nayak@amd.com, huschle@linux.ibm.com, srikar@linux.ibm.com, linux-kernel@vger.kernel.org, christophe.leroy@csgroup.eu, linuxppc-dev@lists.ozlabs.org, gregkh@linuxfoundation.org Subject: [RFC v2 6/9] sched/core: Push current task out if CPU is marked as avoid Date: Thu, 26 Jun 2025 00:41:05 +0530 Message-ID: <20250625191108.1646208-7-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250625191108.1646208-1-sshegde@linux.ibm.com> References: <20250625191108.1646208-1-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-Authority-Analysis: v=2.4 cv=M5FNKzws c=1 sm=1 tr=0 ts=685c49fd cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=6IFa9wvqVegA:10 a=VnNF1IyMAAAA:8 a=Dot9ObxFTPmaUP2n-pkA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjI1MDE0MSBTYWx0ZWRfX+CuQ7G4MP4RS 0BCK6pMAExM4hCUec36PEznclWOD/wJGxt77Alg7NG66bfJbExACF9w6m0ODCOlMVUmSrHWCXT2 CsgDQtKhYufgFvb54qhatEs1gWjTIWq6hdV9EtTqKW/53LnXSXczfmYhFFYYgag9RyPLlewx2Cc UVX1T1NkUvJvdwqZ1Xn0tjZqwBMUng1qN+dvEQTTikPakt/wz5qAVOFqvS/9oMVEvMcG1ysbagw cZl0uzUCXD6Ed2WhGu+u60V6dypIgbVt8ZMC/DkBJVh6ycqeQJmj0KW6Om7PNj83bFoYGUUzV8Z 8T9nokAUpjccyNanJYQiqROLf6qGiZFeYj8y2g1+ZZpwfmG+o+2N0X9bhff9RVGt7S9w2cprKRF mxijQIJfVYlOBc7rEDN08UeF/cHrwU4SncP0Q+MYsyJ34fpzjFzGtAzeZ0vAud/EUbUVXiaZ X-Proofpoint-GUID: V_KS9G9PtvUsA8fgxKxwlLHmIXl9DBl_ X-Proofpoint-ORIG-GUID: zNTvoP9J2-vGjp_xxArM_75tWYqFc7R0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-06-25_06,2025-06-25_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 impostorscore=0 suspectscore=0 priorityscore=1501 phishscore=0 spamscore=0 clxscore=1011 adultscore=0 mlxscore=0 mlxlogscore=999 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2506250141 Actively push out any task running on a CPU marked as avoid. If a task is sleeping it is pushed out if it wakes up on that CPU. Since the task is running, need to use the stopper class to push the task out. Use __balance_push_cpu_stop to achieve that. This currently works only CFS and RT. Signed-off-by: Shrikanth Hegde --- kernel/sched/core.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ kernel/sched/sched.h | 1 + 2 files changed, 45 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 13e44d7a0b90..aea4232e3ec4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5577,6 +5577,10 @@ void sched_tick(void) sched_clock_tick(); + /* push the current task out if cpu is marked as avoid */ + if (cpu_avoid(cpu)) + push_current_task(rq); + rq_lock(rq, &rf); donor = rq->donor; @@ -8028,6 +8032,43 @@ static void balance_hotplug_wait(void) TASK_UNINTERRUPTIBLE); } +static DEFINE_PER_CPU(struct cpu_stop_work, push_task_work); + +/* A CPU is marked as Avoid when there is contention for underlying + * physical CPU and using this CPU will lead to hypervisor preemptions. + * It is better not to use this CPU. + * + * In case any task is scheduled on such CPU, move it out. In + * select_fallback_rq a non_avoid CPU will be chosen and henceforth + * task shouldn't come back to this CPU + */ +void push_current_task(struct rq *rq) +{ + struct task_struct *push_task = rq->curr; + unsigned long flags; + + /* idle task can't be pused out */ + if (rq->curr == rq->idle || !cpu_avoid(rq->cpu)) + return; + + /* Do for only SCHED_NORMAL AND RT for now */ + if (push_task->sched_class != &fair_sched_class && + push_task->sched_class != &rt_sched_class) + return; + + if (kthread_is_per_cpu(push_task) || + is_migration_disabled(push_task)) + return; + + local_irq_save(flags); + get_task_struct(push_task); + preempt_disable(); + + stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task, + this_cpu_ptr(&push_task_work)); + preempt_enable(); + local_irq_restore(flags); +} #else /* !CONFIG_HOTPLUG_CPU: */ static inline void balance_push(struct rq *rq) @@ -8042,6 +8083,9 @@ static inline void balance_hotplug_wait(void) { } +void push_current_task(struct rq *rq) +{ +} #endif /* !CONFIG_HOTPLUG_CPU */ void set_rq_online(struct rq *rq) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 105190b18020..b9614873762e 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1709,6 +1709,7 @@ struct rq_flags { }; extern struct balance_callback balance_push_callback; +void push_current_task(struct rq *rq); #ifdef CONFIG_SCHED_CLASS_EXT extern const struct sched_class ext_sched_class; -- 2.43.0