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authorCyril Hrubis <chrubis@suse.cz>2023-10-02 13:55:52 +0200
committerIngo Molnar <mingo@kernel.org>2023-10-02 15:17:13 +0200
commite6dbdd8fb75526b01787050087b65d12c76b3666 (patch)
tree05f00fdb0bad2aa76352eff253b4ee68606514f9
parent079be8fc630943d9fc70a97807feb73d169ee3fc (diff)
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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.rst14
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.