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| author | Cyril Hrubis <chrubis@suse.cz> | 2023-10-02 13:55:52 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-10-02 15:17:13 +0200 |
| commit | e6dbdd8fb75526b01787050087b65d12c76b3666 (patch) | |
| tree | 05f00fdb0bad2aa76352eff253b4ee68606514f9 | |
| parent | 079be8fc630943d9fc70a97807feb73d169ee3fc (diff) | |
| download | linux-e6dbdd8fb75526b01787050087b65d12c76b3666.tar.gz linux-e6dbdd8fb75526b01787050087b65d12c76b3666.tar.bz2 linux-e6dbdd8fb75526b01787050087b65d12c76b3666.zip | |
sched/rt/docs: Clarify & fix sched_rt_* sysctl docs
- Describe explicitly that sched_rt_runtime_us is allocated from
sched_rt_period_us and hence always less or equal to that value.
- The limit for sched_rt_runtime_us is not INT_MAX-1, but rather it's
limited by the value of sched_rt_period_us. If sched_rt_period_us is
INT_MAX then sched_rt_runtime_us can be set to INT_MAX as well.
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231002115553.3007-3-chrubis@suse.cz
| -rw-r--r-- | Documentation/scheduler/sched-rt-group.rst | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/Documentation/scheduler/sched-rt-group.rst b/Documentation/scheduler/sched-rt-group.rst index 655a096ec8fb..a16bee8f74c2 100644 --- a/Documentation/scheduler/sched-rt-group.rst +++ b/Documentation/scheduler/sched-rt-group.rst @@ -87,18 +87,20 @@ lack an EDF scheduler to make non-uniform periods usable. The system wide settings are configured under the /proc virtual file system: /proc/sys/kernel/sched_rt_period_us: - The scheduling period that is equivalent to 100% CPU bandwidth + The scheduling period that is equivalent to 100% CPU bandwidth. /proc/sys/kernel/sched_rt_runtime_us: - A global limit on how much time realtime scheduling may use. Even without - CONFIG_RT_GROUP_SCHED enabled, this will limit time reserved to realtime - processes. With CONFIG_RT_GROUP_SCHED it signifies the total bandwidth - available to all realtime groups. + A global limit on how much time realtime scheduling may use. This is always + less or equal to the period_us, as it denotes the time allocated from the + period_us for the realtime tasks. Even without CONFIG_RT_GROUP_SCHED enabled, + this will limit time reserved to realtime processes. With + CONFIG_RT_GROUP_SCHED=y it signifies the total bandwidth available to all + realtime groups. * Time is specified in us because the interface is s32. This gives an operating range from 1us to about 35 minutes. * sched_rt_period_us takes values from 1 to INT_MAX. - * sched_rt_runtime_us takes values from -1 to (INT_MAX - 1). + * sched_rt_runtime_us takes values from -1 to sched_rt_period_us. * A run time of -1 specifies runtime == period, ie. no limit. |