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b=vTw97Q1B/fRVuKssdsvIS+Ri/7XpbKSyC4XuaQ+OftLu+McpAL/GJeSosoHDDtdZh5S+vtOO/ZqoCXV3igTHaEn7ZboaVbuhAwIvo5izrwdmEqk/hmGqNby3rEa5gA3A6qYssEV0W91hBxEJ/XbRHRCfsYa5psixD/Pz0iEjMHY= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from CH3PR12MB8658.namprd12.prod.outlook.com (2603:10b6:610:175::8) by PH7PR12MB7843.namprd12.prod.outlook.com (2603:10b6:510:27e::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8880.17; Tue, 1 Jul 2025 03:59:16 +0000 Received: from CH3PR12MB8658.namprd12.prod.outlook.com ([fe80::d5cc:cc84:5e00:2f42]) by CH3PR12MB8658.namprd12.prod.outlook.com ([fe80::d5cc:cc84:5e00:2f42%4]) with mapi id 15.20.8880.027; Tue, 1 Jul 2025 03:59:16 +0000 Message-ID: <30b55100-d903-471f-acf0-12bfc31b0c9a@amd.com> Date: Tue, 1 Jul 2025 09:29:10 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V6 3/7] Sched: Tunable to specify duration of time slice extension To: Prakash Sangappa , linux-kernel@vger.kernel.org Cc: peterz@infradead.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, bigeasy@linutronix.de, vineethr@linux.ibm.com References: <20250701003749.50525-1-prakash.sangappa@oracle.com> <20250701003749.50525-4-prakash.sangappa@oracle.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20250701003749.50525-4-prakash.sangappa@oracle.com> Content-Type: text/plain; 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Setting it to 0, disables scheduler time slice extension. > > Signed-off-by: Prakash Sangappa > --- > v5 -> v6 > - Added documentation for tunable 'sysctl_sched_preempt_delay_us'. > --- > .../admin-guide/kernel-parameters.txt | 8 ++++ > include/linux/sched.h | 5 +++ > include/uapi/linux/rseq.h | 5 ++- > kernel/rseq.c | 7 +++- > kernel/sched/core.c | 40 +++++++++++++++++++ > 5 files changed, 61 insertions(+), 4 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 0ee6c5314637..1e0f86cda0db 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -6398,6 +6398,14 @@ > > sched_verbose [KNL,EARLY] Enables verbose scheduler debug messages. > > + sched_preempt_delay_us= [KNL] > + Scheduler preemption delay in microseconds. > + Allowed range is 0 to 100us. A thread can request > + extending its scheduler time slice on the cpu by > + delaying preemption. Duration of preemption delay > + granted is specified by this parameter. Setting it > + to 0 will disable this feature. > + Shouldn't these bits go into Documentation/admin-guide/sysctl/kernel.rst since this is a sysctl and not a kernel parameter? > schedstats= [KNL,X86] Enable or disable scheduled statistics. > Allowed values are enable and disable. This feature > incurs a small amount of overhead in the scheduler [..snip..] > @@ -4678,6 +4689,24 @@ static int sysctl_schedstats(const struct ctl_table *table, int write, void *buf > #endif /* CONFIG_PROC_SYSCTL */ > #endif /* CONFIG_SCHEDSTATS */ > > +#ifdef CONFIG_PROC_SYSCTL > +#ifdef CONFIG_RSEQ > +static int sysctl_sched_preempt_delay(const struct ctl_table *table, int write, > + void *buffer, size_t *lenp, loff_t *ppos) > +{ > + int err; > + > + err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); > + if (err < 0) > + return err; > + if (sysctl_sched_preempt_delay_us > SCHED_PREEMPT_DELAY_DEFAULT_US) > + pr_warn("Sched preemption delay time set higher then default value %d us\n", s/then/than the/ Should we print the current value too? That way, the dmesg can read how badly the user wanted to shoot themselves in the foot if this ever goes sideways / has unintended effects on PREEMPT_RT. > + SCHED_PREEMPT_DELAY_DEFAULT_US); > + return err; > +} > +#endif /* CONFIG_RSEQ */ > +#endif /* CONFIG_PROC_SYSCTL */ > + > #ifdef CONFIG_SYSCTL > static const struct ctl_table sched_core_sysctls[] = { > #ifdef CONFIG_SCHEDSTATS -- Thanks and Regards, Prateek