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Wed, 19 Nov 2025 06:22:05 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6972920043; Wed, 19 Nov 2025 06:22:05 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6A44820040; Wed, 19 Nov 2025 06:22:01 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.39.25.220]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 19 Nov 2025 06:22:01 +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 08/17] sched/rt: Don't select paravirt CPU for wakeup and push/pull rt task Date: Wed, 19 Nov 2025 11:50:51 +0530 Message-ID: <20251119062100.1112520-9-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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=C/nkCAP+ c=1 sm=1 tr=0 ts=691d6212 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=2Scwftyo7L3m9cOp47sA:9 X-Proofpoint-GUID: GhGYJbtrug5W5sezDSlLEgxqud-X_Off X-Proofpoint-ORIG-GUID: UhACJ7BTkEdsSuImjiVivNYI4j3gD3cA X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfXwzXpbqspGw8t TqTh+kf0BLhovPPpd8ZqZzvk8LJ3S1otv91OVf36CR+Zrw3zvU0LHhJu2pLudL/FSfsfAFFblbc Cu52u/VS/LhvgVZTLA7/T9u3gHQ6+gy5JGbn0jz9IxR/vb+RLKUeMoTv1yqqYd6f5mU+7YMJww8 W9hKv/DN+tBsr3ABIjil+ujCKrRw6lrwVB5PgJX/wW4Z5sSGNTl0xaJWg31f4KCE+qxtFbfH4uy OX/rEnRMG5d/+1CLLx/CB2LVPcvSaErvj5NjrkWK1y1FwKyqLErT9UQBmpN88sCFQ9S0LuDjzvM 4vRhyPpngDzWAOHXftZxRBmphCi8DdaOXvFpL0wXitiLKVmo39LXCKimn8k/i3H/XacvUT0TorR Mt1Kl1DYG63qn7B2scQOO8xW2V3uXw== 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 phishscore=0 priorityscore=1501 spamscore=0 impostorscore=0 bulkscore=0 malwarescore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 Content-Type: text/plain; charset="utf-8" For RT class, - During wakeup don't select a paravirt CPU. - Don't pull a task towards a paravirt CPU. - Don't push a task to a paravirt CPU. Signed-off-by: Shrikanth Hegde --- kernel/sched/rt.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index f1867fe8e5c5..0b78c74dbbe3 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1552,6 +1552,9 @@ select_task_rq_rt(struct task_struct *p, int cpu, int= flags) if (!test && target !=3D -1 && !rt_task_fits_capacity(p, target)) goto out_unlock; =20 + /* Avoid moving to a paravirt CPU */ + if (cpu_paravirt(target)) + goto out_unlock; /* * Don't bother moving it if the destination CPU is * not running a lower priority task. @@ -1876,7 +1879,7 @@ static struct rq *find_lock_lowest_rq(struct task_str= uct *task, struct rq *rq) for (tries =3D 0; tries < RT_MAX_TRIES; tries++) { cpu =3D find_lowest_rq(task); =20 - if ((cpu =3D=3D -1) || (cpu =3D=3D rq->cpu)) + if ((cpu =3D=3D -1) || (cpu =3D=3D rq->cpu) || cpu_paravirt(cpu)) break; =20 lowest_rq =3D cpu_rq(cpu); @@ -1974,7 +1977,7 @@ static int push_rt_task(struct rq *rq, bool pull) return 0; =20 cpu =3D find_lowest_rq(rq->curr); - if (cpu =3D=3D -1 || cpu =3D=3D rq->cpu) + if (cpu =3D=3D -1 || cpu =3D=3D rq->cpu || cpu_paravirt(cpu)) return 0; =20 /* @@ -2237,6 +2240,10 @@ static void pull_rt_task(struct rq *this_rq) if (likely(!rt_overload_count)) return; =20 + /* There is no point in pulling the task towards a paravirt cpu */ + if (cpu_paravirt(this_rq->cpu)) + return; + /* * Match the barrier from rt_set_overloaded; this guarantees that if we * see overloaded we must also see the rto_mask bit. --=20 2.47.3