€•óq      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Portuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/pt_BR/scheduler/sched-rt-group”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”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$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒReal-Time group scheduling”h]”hŒReal-Time group scheduling”…””}”(hh¼h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhh·h²hh³ŒF/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hÍsbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1hËhh·h²hh³hÊh´Kubh¶)”}”(hhh]”(h»)”}”(hŒ
0. WARNING”h]”hŒ
0. WARNING”…””}”(hhàh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhhÝh²hh³hÊh´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höh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Khhðubah}”(h]”h ]”h"]”h$]”h&]”uh1hîh³hÊh´KhhÝh²hubhõ)”}”(hŒMost notable:”h]”hŒMost notable:”…””}”(hj
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KhhÝh²hubhï)”}”(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]”hõ)”}”(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'  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Khj#  ubah}”(h]”h ]”h"]”h$]”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]”hõ)”}”(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?  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Khj;  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ*”uh1j  h³hÊh´Khj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hîh³hÊh´KhhÝh²hubeh}”(h]”Œwarning”ah ]”h"]”Œ
0. warning”ah$]”h&]”uh1hµhh·h²hh³hÊh´Kubh¶)”}”(hhh]”(h»)”}”(hŒ1. Overview”h]”hŒ1. Overview”…””}”(hjl  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhji  h²hh³hÊh´K$ubh¶)”}”(hhh]”(h»)”}”(hŒ1.1 The problem”h]”hŒ1.1 The problem”…””}”(hj}  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhjz  h²hh³hÊh´K(ubhõ)”}”(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j‹  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K*hjz  h²hubeh}”(h]”Œthe-problem”ah ]”h"]”Œ1.1 the problem”ah$]”h&]”uh1hµhji  h²hh³hÊh´K(ubh¶)”}”(hhh]”(h»)”}”(hŒ1.2 The solution”h]”hŒ1.2 The solution”…””}”(hj¤  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj¡  h²hh³hÊh´K2ubhõ)”}”(hŒÔCPU time is divided by means of specifying how much time can be spent running
in a given period. We allocate this "run time" for each real-time group which
the other real-time groups will not be permitted to use.”h]”hŒØCPU time is divided by means of specifying how much time can be spent running
in a given period. We allocate this â€œrun timeâ€ for each real-time group which
the other real-time groups will not be permitted to use.”…””}”(hj²  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K4hj¡  h²hubhõ)”}”(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jÀ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K8hj¡  h²hubhõ)”}”(hXI  Let's consider an example: a frame fixed real-time renderer must deliver 25
frames a second, which yields a period of 0.04s per frame. Now say it will also
have to play some music and respond to input, leaving it with around 80% CPU
time dedicated for the graphics. We can then give this group a run time of 0.8
* 0.04s = 0.032s.”h]”hXK  Letâ€™s consider an example: a frame fixed real-time renderer must deliver 25
frames a second, which yields a period of 0.04s per frame. Now say it will also
have to play some music and respond to input, leaving it with around 80% CPU
time dedicated for the graphics. We can then give this group a run time of 0.8
* 0.04s = 0.032s.”…””}”(hjÎ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K<hj¡  h²hubhõ)”}”(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jÜ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KBhj¡  h²hubhõ)”}”(hŒáThe remaining CPU time will be used for user input and other tasks. Because
real-time tasks have explicitly allocated the CPU time they need to perform
their tasks, buffer underruns in the graphics or audio can be eliminated.”h]”hŒáThe remaining CPU time will be used for user input and other tasks. Because
real-time tasks have explicitly allocated the CPU time they need to perform
their tasks, buffer underruns in the graphics or audio can be eliminated.”…””}”(hjê  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KHhj¡  h²hubhõ)”}”(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jø  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KLhj¡  h²hubeh}”(h]”Œthe-solution”ah ]”h"]”Œ1.2 the solution”ah$]”h&]”uh1hµhji  h²hh³hÊh´K2ubeh}”(h]”Œoverview”ah ]”h"]”Œ1. overview”ah$]”h&]”uh1hµhh·h²hh³hÊh´K$ubh¶)”}”(hhh]”(h»)”}”(hŒ2. The Interface”h]”hŒ2. The Interface”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj  h²hh³hÊh´KQubh¶)”}”(hhh]”(h»)”}”(hŒ2.1 System wide settings”h]”hŒ2.1 System wide settings”…””}”(hj*  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj'  h²hh³hÊh´KUubhõ)”}”(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j8  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KWhj'  h²hubhŒdefinition_list”“”)”}”(hhh]”(hŒdefinition_list_item”“”)”}”(hŒe/proc/sys/kernel/sched_rt_period_us:
The scheduling period that is equivalent to 100% CPU bandwidth.
”h]”(hŒterm”“”)”}”(hŒ$/proc/sys/kernel/sched_rt_period_us:”h]”hŒ$/proc/sys/kernel/sched_rt_period_us:”…””}”(hjS  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jQ  h³hÊh´KZhjM  ubhŒ
definition”“”)”}”(hhh]”hõ)”}”(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jf  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KZhjc  ubah}”(h]”h ]”h"]”h$]”h&]”uh1ja  hjM  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jK  h³hÊh´KZhjH  ubjL  )”}”(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]”(jR  )”}”(hŒ%/proc/sys/kernel/sched_rt_runtime_us:”h]”hŒ%/proc/sys/kernel/sched_rt_runtime_us:”…””}”(hj„  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jQ  h³hÊh´Klhj€  ubjb  )”}”(hhh]”(hõ)”}”(hX€  A global limit on how much time real-time scheduling may use. This is always
less or equal to the period_us, as it denotes the time allocated from the
period_us for the real-time tasks. Without CONFIG_RT_GROUP_SCHED enabled,
this only serves for admission control of deadline tasks. With
CONFIG_RT_GROUP_SCHED=y it also signifies the total bandwidth available to
all real-time groups.”h]”hX€  A global limit on how much time real-time scheduling may use. This is always
less or equal to the period_us, as it denotes the time allocated from the
period_us for the real-time tasks. Without CONFIG_RT_GROUP_SCHED enabled,
this only serves for admission control of deadline tasks. With
CONFIG_RT_GROUP_SCHED=y it also signifies the total bandwidth available to
all real-time groups.”…””}”(hj•  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´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]”hõ)”}”(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jª  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kdhj¦  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hj£  ubj"  )”}”(hŒ2sched_rt_period_us takes values from 1 to INT_MAX.”h]”hõ)”}”(hjÀ  h]”hŒ2sched_rt_period_us takes values from 1 to INT_MAX.”…””}”(hjÂ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kfhj¾  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hj£  ubj"  )”}”(hŒ?sched_rt_runtime_us takes values from -1 to sched_rt_period_us.”h]”hõ)”}”(hj×  h]”hŒ?sched_rt_runtime_us takes values from -1 to sched_rt_period_us.”…””}”(hjÙ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KghjÕ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hj£  ubj"  )”}”(hŒ;A run time of -1 specifies runtime == period, ie. no limit.”h]”hõ)”}”(hjî  h]”hŒ;A run time of -1 specifies runtime == period, ie. no limit.”…””}”(hjð  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Khhjì  ubah}”(h]”h ]”h"]”h$]”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]”hõ)”}”(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j  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kihj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hj£  ubeh}”(h]”h ]”h"]”h$]”h&]”jY  jZ  uh1j  h³hÊh´Kdhj’  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1ja  hj€  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jK  h³hÊh´KlhjH  h²hubeh}”(h]”h ]”h"]”h$]”h&]”uh1jF  hj'  h²hh³hÊh´Nubeh}”(h]”Œsystem-wide-settings”ah ]”h"]”Œ2.1 system wide settings”ah$]”h&]”uh1hµhj  h²hh³hÊh´KUubh¶)”}”(hhh]”(h»)”}”(hŒ2.2 Default behaviour”h]”hŒ2.2 Default behaviour”…””}”(hj>  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj;  h²hh³hÊh´Koubhõ)”}”(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jL  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kqhj;  h²hubhõ)”}”(hX!  By default all bandwidth is assigned to the root group and new groups get the
period from /proc/sys/kernel/sched_rt_period_us and a run time of 0. If you
want to assign bandwidth to another group, reduce the root group's bandwidth
and assign some or all of the difference to another group.”h]”hX#  By default all bandwidth is assigned to the root group and new groups get the
period from /proc/sys/kernel/sched_rt_period_us and a run time of 0. If you
want to assign bandwidth to another group, reduce the root groupâ€™s bandwidth
and assign some or all of the difference to another group.”…””}”(hjZ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kwhj;  h²hubhõ)”}”(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jh  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K|hj;  h²hubeh}”(h]”Œdefault-behaviour”ah ]”h"]”Œ2.2 default behaviour”ah$]”h&]”uh1hµhj  h²hh³hÊh´Koubh¶)”}”(hhh]”(h»)”}”(hŒ2.3 Basis for grouping tasks”h]”hŒ2.3 Basis for grouping tasks”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj~  h²hh³hÊh´K„ubhõ)”}”(hŒ^Enabling CONFIG_RT_GROUP_SCHED lets you explicitly allocate real
CPU bandwidth to task groups.”h]”hŒ^Enabling CONFIG_RT_GROUP_SCHED lets you explicitly allocate real
CPU bandwidth to task groups.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K†hj~  h²hubhõ)”}”(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  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K‰hj~  h²hubhõ)”}”(hŒ}For more information on working with control groups, you should read
Documentation/admin-guide/cgroup-v1/cgroups.rst as well.”h]”hŒ}For more information on working with control groups, you should read
Documentation/admin-guide/cgroup-v1/cgroups.rst as well.”…””}”(hj«  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KŒhj~  h²hubhõ)”}”(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j¹  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Khj~  h²hubhï)”}”(hŒG\Sum_{i} runtime_{i} / global_period <= global_runtime / global_period
”h]”hõ)”}”(hŒF\Sum_{i} runtime_{i} / global_period <= global_runtime / global_period”h]”hŒF Sum_{i} runtime_{i} / global_period <= global_runtime / global_period”…””}”(hjË  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K’hjÇ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hîh³hÊh´K’hj~  h²hubhõ)”}”(hŒMFor now, this can be simplified to just the following (but see Future plans):”h]”hŒMFor now, this can be simplified to just the following (but see Future plans):”…””}”(hjß  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K”hj~  h²hubhï)”}”(hŒ(\Sum_{i} runtime_{i} <= global_runtime

”h]”hõ)”}”(hŒ&\Sum_{i} runtime_{i} <= global_runtime”h]”hŒ& Sum_{i} runtime_{i} <= global_runtime”…””}”(hjñ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K–hjí  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hîh³hÊh´K–hj~  h²hubeh}”(h]”Œbasis-for-grouping-tasks”ah ]”h"]”Œ2.3 basis for grouping tasks”ah$]”h&]”uh1hµhj  h²hh³hÊh´K„ubeh}”(h]”Œthe-interface”ah ]”h"]”Œ2. the interface”ah$]”h&]”uh1hµhh·h²hh³hÊh´KQubh¶)”}”(hhh]”(h»)”}”(hŒ3. Future plans”h]”hŒ3. Future plans”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj  h²hh³hÊh´Kšubhõ)”}”(hŒzThere is work in progress to make the scheduling period for each group
("<cgroup>/cpu.rt_period_us") configurable as well.”h]”hŒ~There is work in progress to make the scheduling period for each group
(â€œ<cgroup>/cpu.rt_period_usâ€) configurable as well.”…””}”(hj&  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kœhj  h²hubhõ)”}”(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j4  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´KŸhj  h²hubhõ)”}”(hŒhConsider two sibling groups A and B; both have 50% bandwidth, but A's
period is twice the length of B's.”h]”hŒlConsider two sibling groups A and B; both have 50% bandwidth, but Aâ€™s
period is twice the length of Bâ€™s.”…””}”(hjB  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K£hj  h²hubj  )”}”(hhh]”(j"  )”}”(hŒWgroup A: period=100000us, runtime=50000us

      - this runs for 0.05s once every 0.1s
”h]”(hõ)”}”(hŒ)group A: period=100000us, runtime=50000us”h]”hŒ)group A: period=100000us, runtime=50000us”…””}”(hjW  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K¦hjS  ubhï)”}”(hŒ&- this runs for 0.05s once every 0.1s
”h]”j  )”}”(hhh]”j"  )”}”(hŒ$this runs for 0.05s once every 0.1s
”h]”hõ)”}”(hŒ#this runs for 0.05s once every 0.1s”h]”hŒ#this runs for 0.05s once every 0.1s”…””}”(hjp  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K¨hjl  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hji  ubah}”(h]”h ]”h"]”h$]”h&]”jY  Œ-”uh1j  h³hÊh´K¨hje  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hîh³hÊh´K¨hjS  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j!  hjP  h²hh³hÊh´Nubj"  )”}”(hŒsgroup B: period= 50000us, runtime=25000us

      - this runs for 0.025s twice every 0.1s (or once every 0.05 sec).
”h]”(hõ)”}”(hŒ)group B: period= 50000us, runtime=25000us”h]”hŒ)group B: period= 50000us, runtime=25000us”…””}”(hj›  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´Kªhj—  ubhï)”}”(hŒB- this runs for 0.025s twice every 0.1s (or once every 0.05 sec).
”h]”j  )”}”(hhh]”j"  )”}”(hŒ@this runs for 0.025s twice every 0.1s (or once every 0.05 sec).
”h]”hõ)”}”(hŒ?this runs for 0.025s twice every 0.1s (or once every 0.05 sec).”h]”hŒ?this runs for 0.025s twice every 0.1s (or once every 0.05 sec).”…””}”(hj´  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K¬hj°  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hj­  ubah}”(h]”h ]”h"]”h$]”h&]”jY  jŠ  uh1j  h³hÊh´K¬hj©  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hîh³hÊh´K¬hj—  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j!  hjP  h²hh³hÊh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jY  jZ  uh1j  h³hÊh´K¦hj  h²hubhõ)”}”(hŒ¤This means that currently a while (1) loop in A will run for the full period of
B and can starve B's tasks (assuming they are of lower priority) for a whole
period.”h]”hŒ¦This means that currently a while (1) loop in A will run for the full period of
B and can starve Bâ€™s tasks (assuming they are of lower priority) for a whole
period.”…””}”(hjà  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K®hj  h²hubhõ)”}”(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jî  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K²hj  h²hubhõ)”}”(hXV  Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
the biggest challenge as the current linux PI infrastructure is geared towards
the limited static priority levels 0-99. With deadline scheduling you need to
do deadline inheritance (since priority is inversely proportional to the
deadline delta (deadline - now)).”h]”hXV  Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
the biggest challenge as the current linux PI infrastructure is geared towards
the limited static priority levels 0-99. With deadline scheduling you need to
do deadline inheritance (since priority is inversely proportional to the
deadline delta (deadline - now)).”…””}”(hjü  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K·hj  h²hubhõ)”}”(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j
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hôh³hÊh´K½hj  h²hubeh}”(h]”Œfuture-plans”ah ]”h"]”Œ3. future plans”ah$]”h&]”uh1hµhh·h²hh³hÊh´Kšubeh}”(h]”Œreal-time-group-scheduling”ah ]”h"]”Œreal-time group scheduling”ah$]”h&]”uh1hµhhh²hh³hÊh´Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”hÊuh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(hºNŒ	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”jK  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”hÊŒ_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"  jf  jc  j  j  jž  j›  j  j  j  j  j8  j5  j{  jx  j
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id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
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