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Wed, 25 Jun 2025 19:11:40 +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 4/9] sched/fair: Don't use CPU marked as avoid for wakeup and load balance Date: Thu, 26 Jun 2025 00:41:03 +0530 Message-ID: <20250625191108.1646208-5-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-Proofpoint-GUID: Bkm9rZTZ3Ey8h4d0sez8YChxm-xlEoG3 X-Proofpoint-ORIG-GUID: 7MZ_nsFenaS2xnJn_vxkGEUnLcWuDv4Y X-Authority-Analysis: v=2.4 cv=dd+A3WXe c=1 sm=1 tr=0 ts=685c49f6 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=R63sIUGh8Hs7vTQp:21 a=6IFa9wvqVegA:10 a=VnNF1IyMAAAA:8 a=5kU7IP4gcsCI17dftJ4A:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjI1MDE0MSBTYWx0ZWRfX5hVljC8FRYal oX4WAk1oDGJK7Ne7imfLdzIwmJzQ1hZp8pDe4rLba1ph29HhU8lfB3QE45lHMY1k/XlaYGNHnOe 7w0Y9DpDMNsWahixdh8/VxzYXh4cwe2CVxpGMz9BRUDOMy5Lk8eAY7mDV636Xhw/E19i2CERTox 8aACcIQzhRWuq48jRzRqzcPqoDiFwzHQ7ashyUsPq4hjMnFZHMohBPd6+DvXPfqMkgjuOzdyzYY 3WxsS2wdTCeRL29wOS9SSnL0DoY3+UezNcyVLlNbvsRwaCFwgaIA9dCoakD5mU2toymLota7Gig ZDhmrU8zWFm5DaurlxDun3oTo3Bovy04t9o4bidml3EPFQrZtAVxgFw+d8/PRMsYnTDhja6sNMt PcE+5uT+W0okks7peUD4MAmon/IQWZ+xSpPVvSQdrtIItyRg0Ojfms1TLF2r2NZ1VZSErAuk 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 impostorscore=0 spamscore=0 mlxlogscore=812 priorityscore=1501 mlxscore=0 clxscore=1015 adultscore=0 phishscore=0 lowpriorityscore=0 malwarescore=0 bulkscore=0 suspectscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2506250141 Load balancer shouldn't spread CFS tasks into a CPU marked as Avoid. Remove those CPUs from load balancing decisions. At wakeup, don't select a CPU marked as avoid. Signed-off-by: Shrikanth Hegde --- while tesing didn't see cpu being marked as avoid while new_cpu is. May need some more probing to see if even cpu can be. if so it could lead to crash. kernel/sched/fair.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7e2963efe800..406288aef535 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8546,7 +8546,12 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) } rcu_read_unlock(); - return new_cpu; + /* Don't select a CPU marked as avoid for wakeup */ + if (cpu_avoid(new_cpu)) + return cpu; + else + return new_cpu; + } /* @@ -11662,6 +11667,9 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); + /* Don't spread load into CPUs marked as avoid */ + cpumask_andnot(cpus, cpus, cpu_avoid_mask); + schedstat_inc(sd->lb_count[idle]); redo: -- 2.43.0