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Thu, 24 Jul 2025 16:16:32 +0000 From: Prakash Sangappa To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, bigeasy@linutronix.de, kprateek.nayak@amd.com, vineethr@linux.ibm.com, prakash.sangappa@oracle.com Subject: [PATCH V7 11/11] sched: Add kernel parameter to enable delaying RT threads Date: Thu, 24 Jul 2025 16:16:25 +0000 Message-ID: <20250724161625.2360309-12-prakash.sangappa@oracle.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250724161625.2360309-1-prakash.sangappa@oracle.com> References: <20250724161625.2360309-1-prakash.sangappa@oracle.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-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-07-24_02,2025-07-24_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 adultscore=0 bulkscore=0 suspectscore=0 mlxscore=0 phishscore=0 mlxlogscore=999 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505160000 definitions=main-2507240123 X-Proofpoint-ORIG-GUID: qcf5amgI0M-8jOUIcPA3aKRhEKbVfAPt X-Proofpoint-GUID: qcf5amgI0M-8jOUIcPA3aKRhEKbVfAPt X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzI0MDEyMyBTYWx0ZWRfX6pNsMTKL3WME y1/Xucw43Gq8LzuqVwM4Se1442gKlWUrx9MAXgztxC3uTJeeIlGJsHqQ2zIJTh2nJo9Y+83rdxZ 1YDn3hiTvb/gN3ggJ1Oriqg7yKO4YClWNXzEprC6U03uTlpK0vhExSey7uS5xAVTGYuIhAx1ge/ j3zBEjupX7Jpp8KEyJYboYCzGhQzJrkzVBeyjtFeekWupdWgmbiYgEbwCJD3U6+vyqool4Zz8kE b/bga7Dq7UQVV8bndzAp45yE/mLWqp8IVW0HPWwUZzWwoNL69NuS4D25vbNOzk6MZqFz62MlY/G GvOhWBTgk9u0RE2GKyI0KZkyDNHsda8OPoPlro3q6X7Dkgfq14SP30Ib7L0lpnEHCpwpz1ngZ7L 8B5Ua58zHdpuplp4vcWGI9OrTXGIdHpGMq6ZRFVp/xybIxP/3ZqwFRtluHjMW0hzRKB+09oT X-Authority-Analysis: v=2.4 cv=Ef3IQOmC c=1 sm=1 tr=0 ts=68825c62 b=1 cx=c_pps a=zPCbziy225d3KhSqZt3L1A==:117 a=zPCbziy225d3KhSqZt3L1A==:17 a=Wb1JkmetP80A:10 a=yPCof4ZbAAAA:8 a=I5Alv-pXL9pxttFBygkA:9 cc=ntf awl=host:12061 Content-Type: text/plain; charset="utf-8" Add a kernel parameter to enable or disable delaying a RT thread from being scheduled on the cpu, if a thread running on cpu has requested extending its time slice. Suggested-by: Thomas Gleixner Signed-off-by: Prakash Sangappa --- include/linux/sched.h | 1 + kernel/entry/common.c | 7 ++++++- kernel/sched/core.c | 14 ++++++++++++++ 3 files changed, 21 insertions(+), 1 deletion(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index af3bf1923509..2e65aafeef23 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -412,6 +412,7 @@ static inline void sched_domains_mutex_unlock(void) { } #ifdef CONFIG_RSEQ_RESCHED_DELAY /* Scheduler time slice extension duration */ extern unsigned int sysctl_sched_preempt_delay_us; +extern unsigned int sysctl_sched_delay_rt; #endif =20 struct sched_param { diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 15ddf335ad4a..912565a24cca 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -85,13 +85,18 @@ void __weak arch_do_signal_or_restart(struct pt_regs *r= egs) { } =20 static inline bool rseq_delay_resched(unsigned long ti_work) { + unsigned long tiflag; + if (!IS_ENABLED(CONFIG_RSEQ_RESCHED_DELAY)) return false; =20 if (unlikely(current->rseq_delay_resched !=3D RSEQ_RESCHED_DELAY_PROBE)) return false; =20 - if (!(ti_work & (_TIF_NEED_RESCHED|_TIF_NEED_RESCHED_LAZY))) + tiflag =3D sysctl_sched_delay_rt ? _TIF_NEED_RESCHED|_TIF_NEED_RESCHED_LA= ZY : + _TIF_NEED_RESCHED_LAZY; + + if (!(ti_work & tiflag)) return false; =20 if (__rseq_delay_resched()) { diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e9be8a6b8851..bf16e11a3c27 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -157,6 +157,11 @@ __read_mostly unsigned int sysctl_sched_nr_migrate =3D= SCHED_NR_MIGRATE_BREAK; */ #define SCHED_PREEMPT_DELAY_DEFAULT_US 30 __read_mostly unsigned int sysctl_sched_preempt_delay_us =3D SCHED_PREEMPT= _DELAY_DEFAULT_US; + +/* + * Scheduler time slice extension - Enable delaying RT threads. Disabled b= y default. + */ +__read_mostly unsigned int sysctl_sched_delay_rt =3D 0; #endif =20 __read_mostly int scheduler_running; @@ -4785,6 +4790,15 @@ static const struct ctl_table sched_core_sysctls[] = =3D { .extra1 =3D SYSCTL_ZERO, .extra2 =3D SYSCTL_ONE_HUNDRED, }, + { + .procname =3D "sched_delay_rt", + .data =3D &sysctl_sched_delay_rt, + .maxlen =3D sizeof(unsigned int), + .mode =3D 0644, + .proc_handler =3D proc_dointvec_minmax, + .extra1 =3D SYSCTL_ZERO, + .extra2 =3D SYSCTL_ONE, + }, #endif /* CONFIG_RSEQ_RESCHED_DELAY */ }; static int __init sched_core_sysctl_init(void) --=20 2.43.5