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Sat, 7 Dec 2024 05:24:39 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9847120043; Sat, 7 Dec 2024 05:24:39 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7993520040; Sat, 7 Dec 2024 05:24:34 +0000 (GMT) Received: from linux.ibm.com (unknown [9.39.29.4]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTPS; Sat, 7 Dec 2024 05:24:34 +0000 (GMT) Date: Sat, 7 Dec 2024 10:54:27 +0530 From: Vishal Chourasia To: Srikar Dronamraju Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, sshegde@linux.ibm.com Subject: Re: [PATCH] sched/fair: Fix CPU bandwidth limit bypass during CPU hotplug Message-ID: References: <20241126064812.809903-2-vishalc@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 30aav4PWm6nhizhZQD8ZocSbYknA5Xuf X-Proofpoint-ORIG-GUID: jdyYriSw1xEuQgJl5UfQsIfx8CpeFyuS X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 mlxscore=0 malwarescore=0 adultscore=0 phishscore=0 suspectscore=0 mlxlogscore=987 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412070034 On Fri, Dec 06, 2024 at 02:37:54PM +0530, Srikar Dronamraju wrote: > * Vishal Chourasia [2024-11-26 12:18:13]: > > > CPU controller limits are not properly enforced during CPU hotplug operations, > > particularly during CPU offline. When a CPU goes offline, throttled > > processes are unintentionally being unthrottled across all CPUs in the system, > > allowing them to exceed their assigned quota limits. > > > > > > Signed-off-by: Vishal Chourasia > > --- > > 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 fbdca89c677f..c436e2307e6f 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -6684,7 +6684,8 @@ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) > > list_for_each_entry_rcu(tg, &task_groups, list) { > > struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; > > > > - if (!cfs_rq->runtime_enabled) > > + /* Don't unthrottle an active cfs_rq unnecessarily */ > > Per the patch description, its not just unnecessary but unthrottling is > buggy. Unnecessary would mean its just an overhead. Here we dont want to > unthrottle. Other than that this seems to be fine to me. sure. Also, I missed running the patch against checkpatch.pl Will be sending out v2 with the updates. vishalc > > > + if (!cfs_rq->runtime_enabled || cpumask_test_cpu(cpu_of(rq), cpu_active_mask)) > > continue; > > -- > Thanks and Regards > Srikar Dronamraju