€•§‡      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/trace/osnoise-tracer”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/zh_TW/trace/osnoise-tracer”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/it_IT/trace/osnoise-tracer”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/ja_JP/trace/osnoise-tracer”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/ko_KR/trace/osnoise-tracer”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/sp_SP/trace/osnoise-tracer”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒOSNOISE Tracer”h]”hŒOSNOISE Tracer”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒB/var/lib/git/docbuild/linux/Documentation/trace/osnoise-tracer.rst”h KubhŒ	paragraph”“”)”}”(hXy  In the context of high-performance computing (HPC), the Operating System
Noise (*osnoise*) refers to the interference experienced by an application
due to activities inside the operating system. In the context of Linux,
NMIs, IRQs, SoftIRQs, and any other system thread can cause noise to the
system. Moreover, hardware-related jobs can also cause noise, for example,
via SMIs.”h]”(hŒPIn the context of high-performance computing (HPC), the Operating System
Noise (”…””}”(hh¹hžhhŸNh NubhŒemphasis”“”)”}”(hŒ	*osnoise*”h]”hŒosnoise”…””}”(hhÃhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÁhh¹ubhX   ) refers to the interference experienced by an application
due to activities inside the operating system. In the context of Linux,
NMIs, IRQs, SoftIRQs, and any other system thread can cause noise to the
system. Moreover, hardware-related jobs can also cause noise, for example,
via SMIs.”…””}”(hh¹hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒghwlat_detector is one of the tools used to identify the most complex
source of noise: *hardware noise*.”h]”(hŒVhwlat_detector is one of the tools used to identify the most complex
source of noise: ”…””}”(hhÛhžhhŸNh NubhÂ)”}”(hŒ*hardware noise*”h]”hŒhardware noise”…””}”(hhãhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÁhhÛubhŒ.”…””}”(hhÛhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hX  In a nutshell, the hwlat_detector creates a thread that runs
periodically for a given period. At the beginning of a period, the thread
disables interrupt and starts sampling. While running, the hwlatd
thread reads the time in a loop. As interrupts are disabled, threads,
IRQs, and SoftIRQs cannot interfere with the hwlatd thread. Hence, the
cause of any gap between two different reads of the time roots either on
NMI or in the hardware itself. At the end of the period, hwlatd enables
interrupts and reports the max observed gap between the reads. It also
prints a NMI occurrence counter. If the output does not report NMI
executions, the user can conclude that the hardware is the culprit for
the latency. The hwlat detects the NMI execution by observing
the entry and exit of a NMI.”h]”hX  In a nutshell, the hwlat_detector creates a thread that runs
periodically for a given period. At the beginning of a period, the thread
disables interrupt and starts sampling. While running, the hwlatd
thread reads the time in a loop. As interrupts are disabled, threads,
IRQs, and SoftIRQs cannot interfere with the hwlatd thread. Hence, the
cause of any gap between two different reads of the time roots either on
NMI or in the hardware itself. At the end of the period, hwlatd enables
interrupts and reports the max observed gap between the reads. It also
prints a NMI occurrence counter. If the output does not report NMI
executions, the user can conclude that the hardware is the culprit for
the latency. The hwlat detects the NMI execution by observing
the entry and exit of a NMI.”…””}”(hhûhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hXÅ  The osnoise tracer leverages the hwlat_detector by running a
similar loop with preemption, SoftIRQs and IRQs enabled, thus allowing
all the sources of *osnoise* during its execution. Using the same approach
of hwlat, osnoise takes note of the entry and exit point of any
source of interferences, increasing a per-cpu interference counter. The
osnoise tracer also saves an interference counter for each source of
interference. The interference counter for NMI, IRQs, SoftIRQs, and
threads is increased anytime the tool observes these interferences' entry
events. When a noise happens without any interference from the operating
system level, the hardware noise counter increases, pointing to a
hardware-related noise. In this way, osnoise can account for any
source of interference. At the end of the period, the osnoise tracer
prints the sum of all noise, the max single noise, the percentage of CPU
available for the thread, and the counters for the noise sources.”h]”(hŒ—The osnoise tracer leverages the hwlat_detector by running a
similar loop with preemption, SoftIRQs and IRQs enabled, thus allowing
all the sources of ”…””}”(hj	  hžhhŸNh NubhÂ)”}”(hŒ	*osnoise*”h]”hŒosnoise”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÁhj	  ubhX'   during its execution. Using the same approach
of hwlat, osnoise takes note of the entry and exit point of any
source of interferences, increasing a per-cpu interference counter. The
osnoise tracer also saves an interference counter for each source of
interference. The interference counter for NMI, IRQs, SoftIRQs, and
threads is increased anytime the tool observes these interferencesâ€™ entry
events. When a noise happens without any interference from the operating
system level, the hardware noise counter increases, pointing to a
hardware-related noise. In this way, osnoise can account for any
source of interference. At the end of the period, the osnoise tracer
prints the sum of all noise, the max single noise, the percentage of CPU
available for the thread, and the counters for the noise sources.”…””}”(hj	  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒUsage”h]”hŒUsage”…””}”(hj,  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj)  hžhhŸh¶h K,ubh¸)”}”(hŒ}Write the ASCII text "osnoise" into the current_tracer file of the
tracing system (generally mounted at /sys/kernel/tracing).”h]”hŒWrite the ASCII text â€œosnoiseâ€ into the current_tracer file of the
tracing system (generally mounted at /sys/kernel/tracing).”…””}”(hj:  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K.hj)  hžhubh¸)”}”(hŒFor example::”h]”hŒFor example:”…””}”(hjH  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K1hj)  hžhubhŒliteral_block”“”)”}”(hŒW[root@f32 ~]# cd /sys/kernel/tracing/
[root@f32 tracing]# echo osnoise > current_tracer”h]”hŒW[root@f32 ~]# cd /sys/kernel/tracing/
[root@f32 tracing]# echo osnoise > current_tracer”…””}”hjX  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1jV  hŸh¶h K3hj)  hžhubh¸)”}”(hŒ>It is possible to follow the trace by reading the trace file::”h]”hŒ=It is possible to follow the trace by reading the trace file:”…””}”(hjh  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K6hj)  hžhubjW  )”}”(hXÜ  [root@f32 tracing]# cat trace
# tracer: osnoise
#
#                                _-----=> irqs-off
#                               / _----=> need-resched
#                              | / _---=> hardirq/softirq
#                              || / _--=> preempt-depth                            MAX
#                              || /                                             SINGLE     Interference counters:
#                              ||||               RUNTIME      NOISE   % OF CPU  NOISE    +-----------------------------+
#           TASK-PID      CPU# ||||   TIMESTAMP    IN US       IN US  AVAILABLE  IN US     HW    NMI    IRQ   SIRQ THREAD
#              | |         |   ||||      |           |             |    |            |      |      |      |      |      |
           <...>-859     [000] ....    81.637220: 1000000        190  99.98100       9     18      0   1007     18      1
           <...>-860     [001] ....    81.638154: 1000000        656  99.93440      74     23      0   1006     16      3
           <...>-861     [002] ....    81.638193: 1000000       5675  99.43250     202      6      0   1013     25     21
           <...>-862     [003] ....    81.638242: 1000000        125  99.98750      45      1      0   1011     23      0
           <...>-863     [004] ....    81.638260: 1000000       1721  99.82790     168      7      0   1002     49     41
           <...>-864     [005] ....    81.638286: 1000000        263  99.97370      57      6      0   1006     26      2
           <...>-865     [006] ....    81.638302: 1000000        109  99.98910      21      3      0   1006     18      1
           <...>-866     [007] ....    81.638326: 1000000       7816  99.21840     107      8      0   1016     39     19”h]”hXÜ  [root@f32 tracing]# cat trace
# tracer: osnoise
#
#                                _-----=> irqs-off
#                               / _----=> need-resched
#                              | / _---=> hardirq/softirq
#                              || / _--=> preempt-depth                            MAX
#                              || /                                             SINGLE     Interference counters:
#                              ||||               RUNTIME      NOISE   % OF CPU  NOISE    +-----------------------------+
#           TASK-PID      CPU# ||||   TIMESTAMP    IN US       IN US  AVAILABLE  IN US     HW    NMI    IRQ   SIRQ THREAD
#              | |         |   ||||      |           |             |    |            |      |      |      |      |      |
           <...>-859     [000] ....    81.637220: 1000000        190  99.98100       9     18      0   1007     18      1
           <...>-860     [001] ....    81.638154: 1000000        656  99.93440      74     23      0   1006     16      3
           <...>-861     [002] ....    81.638193: 1000000       5675  99.43250     202      6      0   1013     25     21
           <...>-862     [003] ....    81.638242: 1000000        125  99.98750      45      1      0   1011     23      0
           <...>-863     [004] ....    81.638260: 1000000       1721  99.82790     168      7      0   1002     49     41
           <...>-864     [005] ....    81.638286: 1000000        263  99.97370      57      6      0   1006     26      2
           <...>-865     [006] ....    81.638302: 1000000        109  99.98910      21      3      0   1006     18      1
           <...>-866     [007] ....    81.638326: 1000000       7816  99.21840     107      8      0   1016     39     19”…””}”hjv  sbah}”(h]”h ]”h"]”h$]”h&]”jf  jg  uh1jV  hŸh¶h K8hj)  hžhubh¸)”}”(hŒÐIn addition to the regular trace fields (from TASK-PID to TIMESTAMP), the
tracer prints a message at the end of each period for each CPU that is
running an osnoise/ thread. The osnoise specific fields report:”h]”hŒÐIn addition to the regular trace fields (from TASK-PID to TIMESTAMP), the
tracer prints a message at the end of each period for each CPU that is
running an osnoise/ thread. The osnoise specific fields report:”…””}”(hj„  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KLhj)  hžhubhŒblock_quote”“”)”}”(hXC  - The RUNTIME IN US reports the amount of time in microseconds that
  the osnoise thread kept looping reading the time.
- The NOISE IN US reports the sum of noise in microseconds observed
  by the osnoise tracer during the associated runtime.
- The % OF CPU AVAILABLE reports the percentage of CPU available for
  the osnoise thread during the runtime window.
- The MAX SINGLE NOISE IN US reports the maximum single noise observed
  during the runtime window.
- The Interference counters display how many each of the respective
  interference happened during the runtime window.
”h]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒsThe RUNTIME IN US reports the amount of time in microseconds that
the osnoise thread kept looping reading the time.”h]”h¸)”}”(hŒsThe RUNTIME IN US reports the amount of time in microseconds that
the osnoise thread kept looping reading the time.”h]”hŒsThe RUNTIME IN US reports the amount of time in microseconds that
the osnoise thread kept looping reading the time.”…””}”(hj£  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KPhjŸ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjš  ubjž  )”}”(hŒvThe NOISE IN US reports the sum of noise in microseconds observed
by the osnoise tracer during the associated runtime.”h]”h¸)”}”(hŒvThe NOISE IN US reports the sum of noise in microseconds observed
by the osnoise tracer during the associated runtime.”h]”hŒvThe NOISE IN US reports the sum of noise in microseconds observed
by the osnoise tracer during the associated runtime.”…””}”(hj»  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KRhj·  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjš  ubjž  )”}”(hŒpThe % OF CPU AVAILABLE reports the percentage of CPU available for
the osnoise thread during the runtime window.”h]”h¸)”}”(hŒpThe % OF CPU AVAILABLE reports the percentage of CPU available for
the osnoise thread during the runtime window.”h]”hŒpThe % OF CPU AVAILABLE reports the percentage of CPU available for
the osnoise thread during the runtime window.”…””}”(hjÓ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KThjÏ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjš  ubjž  )”}”(hŒ_The MAX SINGLE NOISE IN US reports the maximum single noise observed
during the runtime window.”h]”h¸)”}”(hŒ_The MAX SINGLE NOISE IN US reports the maximum single noise observed
during the runtime window.”h]”hŒ_The MAX SINGLE NOISE IN US reports the maximum single noise observed
during the runtime window.”…””}”(hjë  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KVhjç  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjš  ubjž  )”}”(hŒsThe Interference counters display how many each of the respective
interference happened during the runtime window.
”h]”h¸)”}”(hŒrThe Interference counters display how many each of the respective
interference happened during the runtime window.”h]”hŒrThe Interference counters display how many each of the respective
interference happened during the runtime window.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KXhjÿ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjš  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1j˜  hŸh¶h KPhj”  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j’  hŸh¶h KPhj)  hžhubh¸)”}”(hŒËNote that the example above shows a high number of HW noise samples.
The reason being is that this sample was taken on a virtual machine,
and the host interference is detected as a hardware interference.”h]”hŒËNote that the example above shows a high number of HW noise samples.
The reason being is that this sample was taken on a virtual machine,
and the host interference is detected as a hardware interference.”…””}”(hj%  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K[hj)  hžhubeh}”(h]”Œusage”ah ]”h"]”Œusage”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K,ubh¢)”}”(hhh]”(h§)”}”(hŒTracer Configuration”h]”hŒTracer Configuration”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj;  hžhhŸh¶h K`ubh¸)”}”(hŒGThe tracer has a set of options inside the osnoise directory, they are:”h]”hŒGThe tracer has a set of options inside the osnoise directory, they are:”…””}”(hjL  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kbhj;  hžhubj“  )”}”(hXÜ  - osnoise/cpus: CPUs at which a osnoise thread will execute.
- osnoise/period_us: the period of the osnoise thread.
- osnoise/runtime_us: how long an osnoise thread will look for noise.
- osnoise/stop_tracing_us: stop the system tracing if a single noise
  higher than the configured value happens. Writing 0 disables this
  option.
- osnoise/stop_tracing_total_us: stop the system tracing if total noise
  higher than the configured value happens. Writing 0 disables this
  option.
- tracing_threshold: the minimum delta between two time() reads to be
  considered as noise, in us. When set to 0, the default value will
  be used, which is currently 1 us.
- osnoise/options: a set of on/off options that can be enabled by
  writing the option name to the file or disabled by writing the option
  name preceded with the 'NO\_' prefix. For example, writing
  NO_OSNOISE_WORKLOAD disables the OSNOISE_WORKLOAD option. The
  special DEAFAULTS option resets all options to the default value.
”h]”j™  )”}”(hhh]”(jž  )”}”(hŒ:osnoise/cpus: CPUs at which a osnoise thread will execute.”h]”h¸)”}”(hjc  h]”hŒ:osnoise/cpus: CPUs at which a osnoise thread will execute.”…””}”(hje  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kdhja  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubjž  )”}”(hŒ4osnoise/period_us: the period of the osnoise thread.”h]”h¸)”}”(hjz  h]”hŒ4osnoise/period_us: the period of the osnoise thread.”…””}”(hj|  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kehjx  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubjž  )”}”(hŒCosnoise/runtime_us: how long an osnoise thread will look for noise.”h]”h¸)”}”(hj‘  h]”hŒCosnoise/runtime_us: how long an osnoise thread will look for noise.”…””}”(hj“  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kfhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubjž  )”}”(hŒŒosnoise/stop_tracing_us: stop the system tracing if a single noise
higher than the configured value happens. Writing 0 disables this
option.”h]”h¸)”}”(hŒŒosnoise/stop_tracing_us: stop the system tracing if a single noise
higher than the configured value happens. Writing 0 disables this
option.”h]”hŒŒosnoise/stop_tracing_us: stop the system tracing if a single noise
higher than the configured value happens. Writing 0 disables this
option.”…””}”(hjª  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kghj¦  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubjž  )”}”(hŒosnoise/stop_tracing_total_us: stop the system tracing if total noise
higher than the configured value happens. Writing 0 disables this
option.”h]”h¸)”}”(hŒosnoise/stop_tracing_total_us: stop the system tracing if total noise
higher than the configured value happens. Writing 0 disables this
option.”h]”hŒosnoise/stop_tracing_total_us: stop the system tracing if total noise
higher than the configured value happens. Writing 0 disables this
option.”…””}”(hjÂ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kjhj¾  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubjž  )”}”(hŒ§tracing_threshold: the minimum delta between two time() reads to be
considered as noise, in us. When set to 0, the default value will
be used, which is currently 1 us.”h]”h¸)”}”(hŒ§tracing_threshold: the minimum delta between two time() reads to be
considered as noise, in us. When set to 0, the default value will
be used, which is currently 1 us.”h]”hŒ§tracing_threshold: the minimum delta between two time() reads to be
considered as noise, in us. When set to 0, the default value will
be used, which is currently 1 us.”…””}”(hjÚ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KmhjÖ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubjž  )”}”(hXA  osnoise/options: a set of on/off options that can be enabled by
writing the option name to the file or disabled by writing the option
name preceded with the 'NO\_' prefix. For example, writing
NO_OSNOISE_WORKLOAD disables the OSNOISE_WORKLOAD option. The
special DEAFAULTS option resets all options to the default value.
”h]”h¸)”}”(hX@  osnoise/options: a set of on/off options that can be enabled by
writing the option name to the file or disabled by writing the option
name preceded with the 'NO\_' prefix. For example, writing
NO_OSNOISE_WORKLOAD disables the OSNOISE_WORKLOAD option. The
special DEAFAULTS option resets all options to the default value.”h]”hXD  osnoise/options: a set of on/off options that can be enabled by
writing the option name to the file or disabled by writing the option
name preceded with the â€˜NO _â€™ prefix. For example, writing
NO_OSNOISE_WORKLOAD disables the OSNOISE_WORKLOAD option. The
special DEAFAULTS option resets all options to the default value.”…””}”(hjò  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kphjî  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj^  ubeh}”(h]”h ]”h"]”h$]”h&]”j  j  uh1j˜  hŸh¶h KdhjZ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j’  hŸh¶h Kdhj;  hžhubeh}”(h]”Œtracer-configuration”ah ]”h"]”Œtracer configuration”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K`ubh¢)”}”(hhh]”(h§)”}”(hŒTracer Options”h]”hŒTracer Options”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h Kwubh¸)”}”(hŒqThe osnoise/options file exposes a set of on/off configuration options for
the osnoise tracer. These options are:”h]”hŒqThe osnoise/options file exposes a set of on/off configuration options for
the osnoise tracer. These options are:”…””}”(hj+  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kyhj  hžhubj“  )”}”(hXõ  - DEFAULTS: reset the options to the default value.
- OSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
  section below).
- PANIC_ON_STOP: call panic() if the tracer stops. This option serves to
  capture a vmcore.
- OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
  workload, allowing only IRQ and hardware-related noise.
- OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
  allowing only NMIs and hardware-related noise, like hwlat tracer.
”h]”j™  )”}”(hhh]”(jž  )”}”(hŒ1DEFAULTS: reset the options to the default value.”h]”h¸)”}”(hjB  h]”hŒ1DEFAULTS: reset the options to the default value.”…””}”(hjD  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K|hj@  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj=  ubjž  )”}”(hŒQOSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
section below).”h]”h¸)”}”(hŒQOSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
section below).”h]”hŒQOSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
section below).”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K}hjW  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj=  ubjž  )”}”(hŒXPANIC_ON_STOP: call panic() if the tracer stops. This option serves to
capture a vmcore.”h]”h¸)”}”(hŒXPANIC_ON_STOP: call panic() if the tracer stops. This option serves to
capture a vmcore.”h]”hŒXPANIC_ON_STOP: call panic() if the tracer stops. This option serves to
capture a vmcore.”…””}”(hjs  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khjo  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj=  ubjž  )”}”(hŒ}OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
workload, allowing only IRQ and hardware-related noise.”h]”h¸)”}”(hŒ}OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
workload, allowing only IRQ and hardware-related noise.”h]”hŒ}OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
workload, allowing only IRQ and hardware-related noise.”…””}”(hj‹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj‡  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj=  ubjž  )”}”(hŒˆOSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
allowing only NMIs and hardware-related noise, like hwlat tracer.
”h]”h¸)”}”(hŒ‡OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
allowing only NMIs and hardware-related noise, like hwlat tracer.”h]”hŒ‡OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
allowing only NMIs and hardware-related noise, like hwlat tracer.”…””}”(hj£  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KƒhjŸ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj=  ubeh}”(h]”h ]”h"]”h$]”h&]”j  j  uh1j˜  hŸh¶h K|hj9  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j’  hŸh¶h K|hj  hžhubeh}”(h]”Œtracer-options”ah ]”h"]”Œtracer options”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kwubh¢)”}”(hhh]”(h§)”}”(hŒAdditional Tracing”h]”hŒAdditional Tracing”…””}”(hjÎ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjË  hžhhŸh¶h K‡ubh¸)”}”(hŒrIn addition to the tracer, a set of tracepoints were added to
facilitate the identification of the osnoise source.”h]”hŒrIn addition to the tracer, a set of tracepoints were added to
facilitate the identification of the osnoise source.”…””}”(hjÜ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‰hjË  hžhubj“  )”}”(hXo  - osnoise:sample_threshold: printed anytime a noise is higher than
  the configurable tolerance_ns.
- osnoise:nmi_noise: noise from NMI, including the duration.
- osnoise:irq_noise: noise from an IRQ, including the duration.
- osnoise:softirq_noise: noise from a SoftIRQ, including the
  duration.
- osnoise:thread_noise: noise from a thread, including the duration.
”h]”j™  )”}”(hhh]”(jž  )”}”(hŒ_osnoise:sample_threshold: printed anytime a noise is higher than
the configurable tolerance_ns.”h]”h¸)”}”(hŒ_osnoise:sample_threshold: printed anytime a noise is higher than
the configurable tolerance_ns.”h]”hŒ_osnoise:sample_threshold: printed anytime a noise is higher than
the configurable tolerance_ns.”…””}”(hjõ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KŒhjñ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjî  ubjž  )”}”(hŒ:osnoise:nmi_noise: noise from NMI, including the duration.”h]”h¸)”}”(hj  h]”hŒ:osnoise:nmi_noise: noise from NMI, including the duration.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KŽhj	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjî  ubjž  )”}”(hŒ=osnoise:irq_noise: noise from an IRQ, including the duration.”h]”h¸)”}”(hj"  h]”hŒ=osnoise:irq_noise: noise from an IRQ, including the duration.”…””}”(hj$  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj   ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjî  ubjž  )”}”(hŒDosnoise:softirq_noise: noise from a SoftIRQ, including the
duration.”h]”h¸)”}”(hŒDosnoise:softirq_noise: noise from a SoftIRQ, including the
duration.”h]”hŒDosnoise:softirq_noise: noise from a SoftIRQ, including the
duration.”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj7  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjî  ubjž  )”}”(hŒCosnoise:thread_noise: noise from a thread, including the duration.
”h]”h¸)”}”(hŒBosnoise:thread_noise: noise from a thread, including the duration.”h]”hŒBosnoise:thread_noise: noise from a thread, including the duration.”…””}”(hjS  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K’hjO  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjî  ubeh}”(h]”h ]”h"]”h$]”h&]”j  j  uh1j˜  hŸh¶h KŒhjê  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j’  hŸh¶h KŒhjË  hžhubh¸)”}”(hXð  Note that all the values are *net values*. For example, if while osnoise
is running, another thread preempts the osnoise thread, it will start a
thread_noise duration at the start. Then, an IRQ takes place, preempting
the thread_noise, starting a irq_noise. When the IRQ ends its execution,
it will compute its duration, and this duration will be subtracted from
the thread_noise, in such a way as to avoid the double accounting of the
IRQ execution. This logic is valid for all sources of noise.”h]”(hŒNote that all the values are ”…””}”(hjs  hžhhŸNh NubhÂ)”}”(hŒ*net values*”h]”hŒ
net values”…””}”(hj{  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÁhjs  ubhXÇ  . For example, if while osnoise
is running, another thread preempts the osnoise thread, it will start a
thread_noise duration at the start. Then, an IRQ takes place, preempting
the thread_noise, starting a irq_noise. When the IRQ ends its execution,
it will compute its duration, and this duration will be subtracted from
the thread_noise, in such a way as to avoid the double accounting of the
IRQ execution. This logic is valid for all sources of noise.”…””}”(hjs  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K”hjË  hžhubh¸)”}”(hŒ7Here is one example of the usage of these tracepoints::”h]”hŒ6Here is one example of the usage of these tracepoints:”…””}”(hj“  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KœhjË  hžhubjW  )”}”(hXÀ    osnoise/8-961     [008] d.h.  5789.857532: irq_noise: local_timer:236 start 5789.857529929 duration 1845 ns
  osnoise/8-961     [008] dNh.  5789.858408: irq_noise: local_timer:236 start 5789.858404871 duration 2848 ns
migration/8-54      [008] d...  5789.858413: thread_noise: migration/8:54 start 5789.858409300 duration 3068 ns
  osnoise/8-961     [008] ....  5789.858413: sample_threshold: start 5789.858404555 duration 8812 ns interferences 2”h]”hXÀ    osnoise/8-961     [008] d.h.  5789.857532: irq_noise: local_timer:236 start 5789.857529929 duration 1845 ns
  osnoise/8-961     [008] dNh.  5789.858408: irq_noise: local_timer:236 start 5789.858404871 duration 2848 ns
migration/8-54      [008] d...  5789.858413: thread_noise: migration/8:54 start 5789.858409300 duration 3068 ns
  osnoise/8-961     [008] ....  5789.858413: sample_threshold: start 5789.858404555 duration 8812 ns interferences 2”…””}”hj¡  sbah}”(h]”h ]”h"]”h$]”h&]”jf  jg  uh1jV  hŸh¶h KžhjË  hžhubh¸)”}”(hXC  In this example, a noise sample of 8 microseconds was reported in the last
line, pointing to two interferences. Looking backward in the trace, the
two previous entries were about the migration thread running after a
timer IRQ execution. The first event is not part of the noise because
it took place one millisecond before.”h]”hXC  In this example, a noise sample of 8 microseconds was reported in the last
line, pointing to two interferences. Looking backward in the trace, the
two previous entries were about the migration thread running after a
timer IRQ execution. The first event is not part of the noise because
it took place one millisecond before.”…””}”(hj¯  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K£hjË  hžhubh¸)”}”(hX>  It is worth noticing that the sum of the duration reported in the
tracepoints is smaller than eight us reported in the sample_threshold.
The reason roots in the overhead of the entry and exit code that happens
before and after any interference execution. This justifies the dual
approach: measuring thread and tracing.”h]”hX>  It is worth noticing that the sum of the duration reported in the
tracepoints is smaller than eight us reported in the sample_threshold.
The reason roots in the overhead of the entry and exit code that happens
before and after any interference execution. This justifies the dual
approach: measuring thread and tracing.”…””}”(hj½  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K©hjË  hžhubeh}”(h]”Œadditional-tracing”ah ]”h"]”Œadditional tracing”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K‡ubh¢)”}”(hhh]”(h§)”}”(hŒ'Running osnoise tracer without workload”h]”hŒ'Running osnoise tracer without workload”…””}”(hjÖ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÓ  hžhhŸh¶h K°ubh¸)”}”(hŒÊBy enabling the osnoise tracer with the NO_OSNOISE_WORKLOAD option set,
the osnoise: tracepoints serve to measure the execution time of
any type of Linux task, free from the interference of other tasks.”h]”hŒÊBy enabling the osnoise tracer with the NO_OSNOISE_WORKLOAD option set,
the osnoise: tracepoints serve to measure the execution time of
any type of Linux task, free from the interference of other tasks.”…””}”(hjä  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K²hjÓ  hžhubeh}”(h]”Œ'running-osnoise-tracer-without-workload”ah ]”h"]”Œ'running osnoise tracer without workload”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K°ubeh}”(h]”Œosnoise-tracer”ah ]”h"]”Œosnoise tracer”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”j%  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”}”(jÿ  jü  j8  j5  j  j  jÈ  jÅ  jÐ  jÍ  j÷  jô  uŒ	nametypes”}”(jÿ  ‰j8  ‰j  ‰jÈ  ‰jÐ  ‰j÷  ‰uh}”(jü  h£j5  j)  j  j;  jÅ  j  jÍ  jË  jô  jÓ  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.