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Wed, 19 Nov 2025 12:45:29 +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: [PATCH 08/17] sched/rt: Don't select paravirt CPU for wakeup and push/pull rt task Date: Wed, 19 Nov 2025 18:14:40 +0530 Message-ID: <20251119124449.1149616-9-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251119124449.1149616-1-sshegde@linux.ibm.com> References: <20251119124449.1149616-1-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: CjgZiGh28N3kLz-6H1TCKptKIClCh7le X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX2StIe5jMcjrU 8JkCEOWL2uH8yPhf2yn4ECYNmiZjfX2oO9GF7KN9I0Fb3qCQAVRAl+6thihvMPPOBrO5k7fdQNx iVNJPfvXGDcVkcM+Cq0l7NsLcmNtC22qW2j/q0KQnDHK9ndbWjqqKadbVgyGdwWdHLpvQ6Fp5F9 SUE0wNXMAsSHGQ8UQ3XQrjilnFVYjoxn4nVvjpAhTEzN85dqzy4zrCqIfW7LlrWnyu365A0LlMe oR4YCMoNwwsRFAiRfe6DM7hp3XI3y+k3yNksuUN+KbNR5BKt+l0kGSV1b6ImdW2FbY/Gv26eYV5 SE/MjKbi9IE+Esg6TOepj87QjjV+j8LV0NrnOw7N8wFsc+a0YpGYPnowUIH7CuqcZ+GSMBvG42N /9qGg1aQ9aGN/bs8hWIKx6z9u9M2yw== X-Proofpoint-ORIG-GUID: Jb856YEj9Bv6Xl77X6GJsQ1ASlrjgxNV X-Authority-Analysis: v=2.4 cv=XtL3+FF9 c=1 sm=1 tr=0 ts=691dbbf4 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=2Scwftyo7L3m9cOp47sA: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_03,2025-11-18_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 bulkscore=0 priorityscore=1501 impostorscore=0 adultscore=0 lowpriorityscore=0 phishscore=0 suspectscore=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 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 != -1 && !rt_task_fits_capacity(p, target)) goto out_unlock; + /* 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_struct *task, struct rq *rq) for (tries = 0; tries < RT_MAX_TRIES; tries++) { cpu = find_lowest_rq(task); - if ((cpu == -1) || (cpu == rq->cpu)) + if ((cpu == -1) || (cpu == rq->cpu) || cpu_paravirt(cpu)) break; lowest_rq = cpu_rq(cpu); @@ -1974,7 +1977,7 @@ static int push_rt_task(struct rq *rq, bool pull) return 0; cpu = find_lowest_rq(rq->curr); - if (cpu == -1 || cpu == rq->cpu) + if (cpu == -1 || cpu == rq->cpu || cpu_paravirt(cpu)) return 0; /* @@ -2237,6 +2240,10 @@ static void pull_rt_task(struct rq *this_rq) if (likely(!rt_overload_count)) return; + /* 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. -- 2.47.3