€•q      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ,/translations/zh_CN/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/zh_TW/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/it_IT/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/ja_JP/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/ko_KR/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/sp_SP/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒReal-Time group scheduling”h]”hŒReal-Time group scheduling”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒF/var/lib/git/docbuild/linux/Documentation/scheduler/sched-rt-group.rst”h KubhŒcomment”“”)”}”(hŒ¸CONTENTS

0. WARNING
1. Overview
  1.1 The problem
  1.2 The solution
2. The interface
  2.1 System-wide settings
  2.2 Default behaviour
  2.3 Basis for grouping tasks
3. Future plans”h]”hŒ¸CONTENTS

0. WARNING
1. Overview
  1.1 The problem
  1.2 The solution
2. The interface
  2.1 System-wide settings
  2.2 Default behaviour
  2.3 Basis for grouping tasks
3. Future plans”…””}”hh¹sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h·hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒ
0. WARNING”h]”hŒ
0. WARNING”…””}”(hhÌhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhÉhžhhŸh¶h KubhŒblock_quote”“”)”}”(hŒ€Fiddling with these settings can result in an unstable system, the knobs are
root only and assumes root knows what he is doing.
”h]”hŒ	paragraph”“”)”}”(hŒFiddling with these settings can result in an unstable system, the knobs are
root only and assumes root knows what he is doing.”h]”hŒFiddling with these settings can result in an unstable system, the knobs are
root only and assumes root knows what he is doing.”…””}”(hhâhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KhhÜubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh¶h KhhÉhžhubhá)”}”(hŒMost notable:”h]”hŒMost notable:”…””}”(hhöhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KhhÉhžhubhÛ)”}”(hXÀ  * very small values in sched_rt_period_us can result in an unstable
  system when the period is smaller than either the available hrtimer
  resolution, or the time it takes to handle the budget refresh itself.

* very small values in sched_rt_runtime_us can result in an unstable
  system when the runtime is so small the system has difficulty making
  forward progress (NOTE: the migration thread and kstopmachine both
  are real-time processes).
”h]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒÌvery small values in sched_rt_period_us can result in an unstable
system when the period is smaller than either the available hrtimer
resolution, or the time it takes to handle the budget refresh itself.
”h]”há)”}”(hŒËvery small values in sched_rt_period_us can result in an unstable
system when the period is smaller than either the available hrtimer
resolution, or the time it takes to handle the budget refresh itself.”h]”hŒËvery small values in sched_rt_period_us can result in an unstable
system when the period is smaller than either the available hrtimer
resolution, or the time it takes to handle the budget refresh itself.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Khj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj
  ubj  )”}”(hŒåvery small values in sched_rt_runtime_us can result in an unstable
system when the runtime is so small the system has difficulty making
forward progress (NOTE: the migration thread and kstopmachine both
are real-time processes).
”h]”há)”}”(hŒävery small values in sched_rt_runtime_us can result in an unstable
system when the runtime is so small the system has difficulty making
forward progress (NOTE: the migration thread and kstopmachine both
are real-time processes).”h]”hŒävery small values in sched_rt_runtime_us can result in an unstable
system when the runtime is so small the system has difficulty making
forward progress (NOTE: the migration thread and kstopmachine both
are real-time processes).”…””}”(hj+  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Khj'  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj
  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ*”uh1j  hŸh¶h Khj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh¶h KhhÉhžhubeh}”(h]”Œwarning”ah ]”h"]”Œ
0. warning”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒ1. Overview”h]”hŒ1. Overview”…””}”(hjX  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjU  hžhhŸh¶h K$ubh¢)”}”(hhh]”(h§)”}”(hŒ1.1 The problem”h]”hŒ1.1 The problem”…””}”(hji  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjf  hžhhŸh¶h K(ubhá)”}”(hXÅ  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 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.”h]”hXÅ  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 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.”…””}”(hjw  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K*hjf  hžhubeh}”(h]”Œthe-problem”ah ]”h"]”Œ1.1 the problem”ah$]”h&]”uh1h¡hjU  hžhhŸh¶h K(ubh¢)”}”(hhh]”(h§)”}”(hŒ1.2 The solution”h]”hŒ1.2 The solution”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h K2ubhá)”}”(hŒÔCPU time is divided by means of specifying how much time can be spent running
in a given period. We allocate this "run time" for each real-time group which
the other real-time groups will not be permitted to use.”h]”hŒØCPU time is divided by means of specifying how much time can be spent running
in a given period. We allocate this â€œrun timeâ€ for each real-time group which
the other real-time groups will not be permitted to use.”…””}”(hjž  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K4hj  hžhubhá)”}”(hŒ«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.”h]”hŒ«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.”…””}”(hj¬  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K8hj  hžhubhá)”}”(hXI  Let's consider an example: a frame fixed real-time renderer must deliver 25
frames a second, which yields a period of 0.04s per frame. Now say it will also
have to play some music and respond to input, leaving it with around 80% CPU
time dedicated for the graphics. We can then give this group a run time of 0.8
* 0.04s = 0.032s.”h]”hXK  Letâ€™s consider an example: a frame fixed real-time renderer must deliver 25
frames a second, which yields a period of 0.04s per frame. Now say it will also
have to play some music and respond to input, leaving it with around 80% CPU
time dedicated for the graphics. We can then give this group a run time of 0.8
* 0.04s = 0.032s.”…””}”(hjº  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K<hj  hžhubhá)”}”(hX@  This way the graphics group will have a 0.04s period with a 0.032s run time
limit. Now if the audio thread needs to refill the DMA buffer every 0.005s, but
needs only about 3% CPU time to do so, it can do with a 0.03 * 0.005s =
0.00015s. So this group can be scheduled with a period of 0.005s and a run time
of 0.00015s.”h]”hX@  This way the graphics group will have a 0.04s period with a 0.032s run time
limit. Now if the audio thread needs to refill the DMA buffer every 0.005s, but
needs only about 3% CPU time to do so, it can do with a 0.03 * 0.005s =
0.00015s. So this group can be scheduled with a period of 0.005s and a run time
of 0.00015s.”…””}”(hjÈ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KBhj  hžhubhá)”}”(hŒáThe remaining CPU time will be used for user input and other tasks. Because
real-time tasks have explicitly allocated the CPU time they need to perform
their tasks, buffer underruns in the graphics or audio can be eliminated.”h]”hŒáThe remaining CPU time will be used for user input and other tasks. Because
real-time tasks have explicitly allocated the CPU time they need to perform
their tasks, buffer underruns in the graphics or audio can be eliminated.”…””}”(hjÖ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KHhj  hžhubhá)”}”(hŒxNOTE: the above example is not fully implemented yet. We still
lack an EDF scheduler to make non-uniform periods usable.”h]”hŒxNOTE: the above example is not fully implemented yet. We still
lack an EDF scheduler to make non-uniform periods usable.”…””}”(hjä  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KLhj  hžhubeh}”(h]”Œthe-solution”ah ]”h"]”Œ1.2 the solution”ah$]”h&]”uh1h¡hjU  hžhhŸh¶h K2ubeh}”(h]”Œoverview”ah ]”h"]”Œ1. overview”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K$ubh¢)”}”(hhh]”(h§)”}”(hŒ2. The Interface”h]”hŒ2. The Interface”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h KQubh¢)”}”(hhh]”(h§)”}”(hŒ2.1 System wide settings”h]”hŒ2.1 System wide settings”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h KUubhá)”}”(hŒLThe system wide settings are configured under the /proc virtual file system:”h]”hŒLThe system wide settings are configured under the /proc virtual file system:”…””}”(hj$  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KWhj  hžhubhŒdefinition_list”“”)”}”(hhh]”(hŒdefinition_list_item”“”)”}”(hŒe/proc/sys/kernel/sched_rt_period_us:
The scheduling period that is equivalent to 100% CPU bandwidth.
”h]”(hŒterm”“”)”}”(hŒ$/proc/sys/kernel/sched_rt_period_us:”h]”hŒ$/proc/sys/kernel/sched_rt_period_us:”…””}”(hj?  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j=  hŸh¶h KZhj9  ubhŒ
definition”“”)”}”(hhh]”há)”}”(hŒ?The scheduling period that is equivalent to 100% CPU bandwidth.”h]”hŒ?The scheduling period that is equivalent to 100% CPU bandwidth.”…””}”(hjR  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KZhjO  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jM  hj9  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j7  hŸh¶h KZhj4  ubj8  )”}”(hXš  /proc/sys/kernel/sched_rt_runtime_us:
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 real-time tasks. Without CONFIG_RT_GROUP_SCHED enabled,
this only serves for admission control of deadline tasks. With
CONFIG_RT_GROUP_SCHED=y it also signifies the total bandwidth available to
all real-time 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 sched_rt_period_us.
* A run time of -1 specifies runtime == period, ie. no limit.
* sched_rt_runtime_us/sched_rt_period_us > 0.05 inorder to preserve
  bandwidth for fair dl_server. For accurate value check average of
  runtime/period in /sys/kernel/debug/sched/fair_server/cpuX/

”h]”(j>  )”}”(hŒ%/proc/sys/kernel/sched_rt_runtime_us:”h]”hŒ%/proc/sys/kernel/sched_rt_runtime_us:”…””}”(hjp  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j=  hŸh¶h Klhjl  ubjN  )”}”(hhh]”(há)”}”(hX€  A global limit on how much time real-time scheduling may use. This is always
less or equal to the period_us, as it denotes the time allocated from the
period_us for the real-time tasks. Without CONFIG_RT_GROUP_SCHED enabled,
this only serves for admission control of deadline tasks. With
CONFIG_RT_GROUP_SCHED=y it also signifies the total bandwidth available to
all real-time groups.”h]”hX€  A global limit on how much time real-time scheduling may use. This is always
less or equal to the period_us, as it denotes the time allocated from the
period_us for the real-time tasks. Without CONFIG_RT_GROUP_SCHED enabled,
this only serves for admission control of deadline tasks. With
CONFIG_RT_GROUP_SCHED=y it also signifies the total bandwidth available to
all real-time groups.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K]hj~  ubj	  )”}”(hhh]”(j  )”}”(hŒqTime is specified in us because the interface is s32. This gives an
operating range from 1us to about 35 minutes.”h]”há)”}”(hŒqTime is specified in us because the interface is s32. This gives an
operating range from 1us to about 35 minutes.”h]”hŒqTime is specified in us because the interface is s32. This gives an
operating range from 1us to about 35 minutes.”…””}”(hj–  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kdhj’  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubj  )”}”(hŒ2sched_rt_period_us takes values from 1 to INT_MAX.”h]”há)”}”(hj¬  h]”hŒ2sched_rt_period_us takes values from 1 to INT_MAX.”…””}”(hj®  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kfhjª  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubj  )”}”(hŒ?sched_rt_runtime_us takes values from -1 to sched_rt_period_us.”h]”há)”}”(hjÃ  h]”hŒ?sched_rt_runtime_us takes values from -1 to sched_rt_period_us.”…””}”(hjÅ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KghjÁ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubj  )”}”(hŒ;A run time of -1 specifies runtime == period, ie. no limit.”h]”há)”}”(hjÚ  h]”hŒ;A run time of -1 specifies runtime == period, ie. no limit.”…””}”(hjÜ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KhhjØ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubj  )”}”(hŒÁsched_rt_runtime_us/sched_rt_period_us > 0.05 inorder to preserve
bandwidth for fair dl_server. For accurate value check average of
runtime/period in /sys/kernel/debug/sched/fair_server/cpuX/

”h]”há)”}”(hŒ¿sched_rt_runtime_us/sched_rt_period_us > 0.05 inorder to preserve
bandwidth for fair dl_server. For accurate value check average of
runtime/period in /sys/kernel/debug/sched/fair_server/cpuX/”h]”hŒ¿sched_rt_runtime_us/sched_rt_period_us > 0.05 inorder to preserve
bandwidth for fair dl_server. For accurate value check average of
runtime/period in /sys/kernel/debug/sched/fair_server/cpuX/”…””}”(hjó  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kihjï  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”jE  jF  uh1j  hŸh¶h Kdhj~  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jM  hjl  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j7  hŸh¶h Klhj4  hžhubeh}”(h]”h ]”h"]”h$]”h&]”uh1j2  hj  hžhhŸh¶h Nubeh}”(h]”Œsystem-wide-settings”ah ]”h"]”Œ2.1 system wide settings”ah$]”h&]”uh1h¡hj  hžhhŸh¶h KUubh¢)”}”(hhh]”(h§)”}”(hŒ2.2 Default behaviour”h]”hŒ2.2 Default behaviour”…””}”(hj*  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj'  hžhhŸh¶h Koubhá)”}”(hX^  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
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.”h]”hX`  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
real-time tasks will not lock up the machine but leave a little time to recover
it.  By setting runtime to -1 youâ€™d get the old behaviour back.”…””}”(hj8  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kqhj'  hžhubhá)”}”(hX!  By default all bandwidth is assigned to the root group and new groups get the
period from /proc/sys/kernel/sched_rt_period_us and a run time of 0. If you
want to assign bandwidth to another group, reduce the root group's bandwidth
and assign some or all of the difference to another group.”h]”hX#  By default all bandwidth is assigned to the root group and new groups get the
period from /proc/sys/kernel/sched_rt_period_us and a run time of 0. If you
want to assign bandwidth to another group, reduce the root groupâ€™s bandwidth
and assign some or all of the difference to another group.”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kwhj'  hžhubhá)”}”(hX>  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!”h]”hX>  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!”…””}”(hjT  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K|hj'  hžhubeh}”(h]”Œdefault-behaviour”ah ]”h"]”Œ2.2 default behaviour”ah$]”h&]”uh1h¡hj  hžhhŸh¶h Koubh¢)”}”(hhh]”(h§)”}”(hŒ2.3 Basis for grouping tasks”h]”hŒ2.3 Basis for grouping tasks”…””}”(hjm  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjj  hžhhŸh¶h K„ubhá)”}”(hŒ^Enabling CONFIG_RT_GROUP_SCHED lets you explicitly allocate real
CPU bandwidth to task groups.”h]”hŒ^Enabling CONFIG_RT_GROUP_SCHED lets you explicitly allocate real
CPU bandwidth to task groups.”…””}”(hj{  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K†hjj  hžhubhá)”}”(hŒ‚This uses the cgroup virtual file system and "<cgroup>/cpu.rt_runtime_us"
to control the CPU time reserved for each control group.”h]”hŒ†This uses the cgroup virtual file system and â€œ<cgroup>/cpu.rt_runtime_usâ€
to control the CPU time reserved for each control group.”…””}”(hj‰  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K‰hjj  hžhubhá)”}”(hŒ}For more information on working with control groups, you should read
Documentation/admin-guide/cgroup-v1/cgroups.rst as well.”h]”hŒ}For more information on working with control groups, you should read
Documentation/admin-guide/cgroup-v1/cgroups.rst as well.”…””}”(hj—  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KŒhjj  hžhubhá)”}”(hŒgGroup settings are checked against the following limits in order to keep the
configuration schedulable:”h]”hŒgGroup settings are checked against the following limits in order to keep the
configuration schedulable:”…””}”(hj¥  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Khjj  hžhubhÛ)”}”(hŒG\Sum_{i} runtime_{i} / global_period <= global_runtime / global_period
”h]”há)”}”(hŒF\Sum_{i} runtime_{i} / global_period <= global_runtime / global_period”h]”hŒF Sum_{i} runtime_{i} / global_period <= global_runtime / global_period”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K’hj³  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh¶h K’hjj  hžhubhá)”}”(hŒMFor now, this can be simplified to just the following (but see Future plans):”h]”hŒMFor now, this can be simplified to just the following (but see Future plans):”…””}”(hjË  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K”hjj  hžhubhÛ)”}”(hŒ(\Sum_{i} runtime_{i} <= global_runtime

”h]”há)”}”(hŒ&\Sum_{i} runtime_{i} <= global_runtime”h]”hŒ& Sum_{i} runtime_{i} <= global_runtime”…””}”(hjÝ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K–hjÙ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh¶h K–hjj  hžhubeh}”(h]”Œbasis-for-grouping-tasks”ah ]”h"]”Œ2.3 basis for grouping tasks”ah$]”h&]”uh1h¡hj  hžhhŸh¶h K„ubeh}”(h]”Œthe-interface”ah ]”h"]”Œ2. the interface”ah$]”h&]”uh1h¡hh£hžhhŸh¶h KQubh¢)”}”(hhh]”(h§)”}”(hŒ3. Future plans”h]”hŒ3. Future plans”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h Kšubhá)”}”(hŒzThere is work in progress to make the scheduling period for each group
("<cgroup>/cpu.rt_period_us") configurable as well.”h]”hŒ~There is work in progress to make the scheduling period for each group
(â€œ<cgroup>/cpu.rt_period_usâ€) configurable as well.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kœhj  hžhubhá)”}”(hŒÆThe constraint on the period is that a subgroup must have a smaller or
equal period to its parent. But realistically its not very useful _yet_
as its prone to starvation without deadline scheduling.”h]”hŒÆThe constraint on the period is that a subgroup must have a smaller or
equal period to its parent. But realistically its not very useful _yet_
as its prone to starvation without deadline scheduling.”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h KŸhj  hžhubhá)”}”(hŒhConsider two sibling groups A and B; both have 50% bandwidth, but A's
period is twice the length of B's.”h]”hŒlConsider two sibling groups A and B; both have 50% bandwidth, but Aâ€™s
period is twice the length of Bâ€™s.”…””}”(hj.  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K£hj  hžhubj	  )”}”(hhh]”(j  )”}”(hŒWgroup A: period=100000us, runtime=50000us

      - this runs for 0.05s once every 0.1s
”h]”(há)”}”(hŒ)group A: period=100000us, runtime=50000us”h]”hŒ)group A: period=100000us, runtime=50000us”…””}”(hjC  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K¦hj?  ubhÛ)”}”(hŒ&- this runs for 0.05s once every 0.1s
”h]”j	  )”}”(hhh]”j  )”}”(hŒ$this runs for 0.05s once every 0.1s
”h]”há)”}”(hŒ#this runs for 0.05s once every 0.1s”h]”hŒ#this runs for 0.05s once every 0.1s”…””}”(hj\  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K¨hjX  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjU  ubah}”(h]”h ]”h"]”h$]”h&]”jE  Œ-”uh1j  hŸh¶h K¨hjQ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh¶h K¨hj?  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj<  hžhhŸh¶h Nubj  )”}”(hŒsgroup B: period= 50000us, runtime=25000us

      - this runs for 0.025s twice every 0.1s (or once every 0.05 sec).
”h]”(há)”}”(hŒ)group B: period= 50000us, runtime=25000us”h]”hŒ)group B: period= 50000us, runtime=25000us”…””}”(hj‡  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h Kªhjƒ  ubhÛ)”}”(hŒB- this runs for 0.025s twice every 0.1s (or once every 0.05 sec).
”h]”j	  )”}”(hhh]”j  )”}”(hŒ@this runs for 0.025s twice every 0.1s (or once every 0.05 sec).
”h]”há)”}”(hŒ?this runs for 0.025s twice every 0.1s (or once every 0.05 sec).”h]”hŒ?this runs for 0.025s twice every 0.1s (or once every 0.05 sec).”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K¬hjœ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj™  ubah}”(h]”h ]”h"]”h$]”h&]”jE  jv  uh1j  hŸh¶h K¬hj•  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh¶h K¬hjƒ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj<  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”jE  jF  uh1j  hŸh¶h K¦hj  hžhubhá)”}”(hŒ¤This means that currently a while (1) loop in A will run for the full period of
B and can starve B's tasks (assuming they are of lower priority) for a whole
period.”h]”hŒ¦This means that currently a while (1) loop in A will run for the full period of
B and can starve Bâ€™s tasks (assuming they are of lower priority) for a whole
period.”…””}”(hjÌ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K®hj  hžhubhá)”}”(hX  The next project will be SCHED_EDF (Earliest Deadline First scheduling) to bring
full deadline scheduling to the linux kernel. Deadline scheduling the above
groups and treating end of the period as a deadline will ensure that they both
get their allocated time.”h]”hX  The next project will be SCHED_EDF (Earliest Deadline First scheduling) to bring
full deadline scheduling to the linux kernel. Deadline scheduling the above
groups and treating end of the period as a deadline will ensure that they both
get their allocated time.”…””}”(hjÚ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K²hj  hžhubhá)”}”(hXV  Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
the biggest challenge as the current linux PI infrastructure is geared towards
the limited static priority levels 0-99. With deadline scheduling you need to
do deadline inheritance (since priority is inversely proportional to the
deadline delta (deadline - now)).”h]”hXV  Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
the biggest challenge as the current linux PI infrastructure is geared towards
the limited static priority levels 0-99. With deadline scheduling you need to
do deadline inheritance (since priority is inversely proportional to the
deadline delta (deadline - now)).”…””}”(hjè  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K·hj  hžhubhá)”}”(hŒxThis means the whole PI machinery will have to be reworked - and that is one of
the most complex pieces of code we have.”h]”hŒxThis means the whole PI machinery will have to be reworked - and that is one of
the most complex pieces of code we have.”…””}”(hjö  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hàhŸh¶h K½hj  hžhubeh}”(h]”Œfuture-plans”ah ]”h"]”Œ3. future plans”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kšubeh}”(h]”Œreal-time-group-scheduling”ah ]”h"]”Œreal-time group scheduling”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j7  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  j  jR  jO  jÿ  jü  jŠ  j‡  j÷  jô  jþ  jû  j$  j!  jg  jd  jö  jó  j	  j  uŒ	nametypes”}”(j  ‰jR  ‰jÿ  ‰jŠ  ‰j÷  ‰jþ  ‰j$  ‰jg  ‰jö  ‰j	  ‰uh}”(j  h£jO  hÉjü  jU  j‡  jf  jô  j  jû  j  j!  j  jd  j'  jó  jj  j  j  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.