@@ -39,10 +39,10 @@ Most notable:
1.1 The problem
---------------
-Realtime scheduling is all about determinism, a group has to be able to rely on
+Real-time scheduling is all about determinism, a group has to be able to rely on
the amount of bandwidth (eg. CPU time) being constant. In order to schedule
-multiple groups of realtime tasks, each group must be assigned a fixed portion
-of the CPU time available. Without a minimum guarantee a realtime group can
+multiple groups of real-time tasks, each group must be assigned a fixed portion
+of the CPU time available. Without a minimum guarantee a real-time group can
obviously fall short. A fuzzy upper limit is of no use since it cannot be
relied upon. Which leaves us with just the single fixed portion.
@@ -50,14 +50,14 @@ relied upon. Which leaves us with just the single fixed portion.
----------------
CPU time is divided by means of specifying how much time can be spent running
-in a given period. We allocate this "run time" for each realtime group which
-the other realtime groups will not be permitted to use.
+in a given period. We allocate this "run time" for each real-time group which
+the other real-time groups will not be permitted to use.
-Any time not allocated to a realtime group will be used to run normal priority
+Any time not allocated to a real-time group will be used to run normal priority
tasks (SCHED_OTHER). Any allocated run time not used will also be picked up by
SCHED_OTHER.
-Let's consider an example: a frame fixed realtime renderer must deliver 25
+Let's consider an example: a frame fixed real-time renderer must deliver 25
frames a second, which yields a period of 0.04s per frame. Now say it will also
have to play some music and respond to input, leaving it with around 80% CPU
time dedicated for the graphics. We can then give this group a run time of 0.8
@@ -70,7 +70,7 @@ needs only about 3% CPU time to do so, it can do with a 0.03 * 0.005s =
of 0.00015s.
The remaining CPU time will be used for user input and other tasks. Because
-realtime tasks have explicitly allocated the CPU time they need to perform
+real-time tasks have explicitly allocated the CPU time they need to perform
their tasks, buffer underruns in the graphics or audio can be eliminated.
NOTE: the above example is not fully implemented yet. We still
@@ -90,12 +90,12 @@ The system wide settings are configured under the /proc virtual file system:
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. This is always
+ A global limit on how much time real-time 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
+ period_us for the real-time tasks. Even without CONFIG_RT_GROUP_SCHED enabled,
+ this will limit time reserved to real-time processes. With
CONFIG_RT_GROUP_SCHED=y it signifies the total bandwidth available to all
- realtime groups.
+ real-time groups.
* Time is specified in us because the interface is s32. This gives an
operating range from 1us to about 35 minutes.
@@ -110,7 +110,7 @@ The system wide settings are configured under the /proc virtual file system:
The default values for sched_rt_period_us (1000000 or 1s) and
sched_rt_runtime_us (950000 or 0.95s). This gives 0.05s to be used by
SCHED_OTHER (non-RT tasks). These defaults were chosen so that a run-away
-realtime tasks will not lock up the machine but leave a little time to recover
+real-time tasks will not lock up the machine but leave a little time to recover
it. By setting runtime to -1 you'd get the old behaviour back.
By default all bandwidth is assigned to the root group and new groups get the
@@ -118,10 +118,10 @@ period from /proc/sys/kernel/sched_rt_period_us and a run time of 0. If you
want to assign bandwidth to another group, reduce the root group's bandwidth
and assign some or all of the difference to another group.
-Realtime group scheduling means you have to assign a portion of total CPU
-bandwidth to the group before it will accept realtime tasks. Therefore you will
-not be able to run realtime tasks as any user other than root until you have
-done that, even if the user has the rights to run processes with realtime
+Real-time group scheduling means you have to assign a portion of total CPU
+bandwidth to the group before it will accept real-time tasks. Therefore you will
+not be able to run real-time tasks as any user other than root until you have
+done that, even if the user has the rights to run processes with real-time
priority!
Signed-off-by: Cyril Hrubis <chrubis@suse.cz> --- Documentation/scheduler/sched-rt-group.rst | 34 +++++++++++----------- 1 file changed, 17 insertions(+), 17 deletions(-)