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trace doc: convert trace/hwlat_detector.txt to rst fromat

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This converts the plain text documentation to reStructuredText format and
add it into Sphinx TOC tree. No essential content change.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Changbin Du 2018-02-17 13:39:48 +08:00 committed by Jonathan Corbet
parent ed657c1cbc
commit 8df2d75e6e
2 changed files with 16 additions and 11 deletions
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26
Documentation/trace/hwlat_detector.txt → Documentation/trace/hwlat_detector.rst
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@ -1,4 +1,8 @@
Introduction: =========================
Hardware Latency Detector
=========================
Introduction
------------- -------------
The tracer hwlat_detector is a special purpose tracer that is used to The tracer hwlat_detector is a special purpose tracer that is used to
@ -28,7 +32,7 @@ Note that the hwlat detector should *NEVER* be used in a production environment.
It is intended to be run manually to determine if the hardware platform has a It is intended to be run manually to determine if the hardware platform has a
problem with long system firmware service routines. problem with long system firmware service routines.
Usage: Usage
------ ------
Write the ASCII text "hwlat" into the current_tracer file of the tracing system Write the ASCII text "hwlat" into the current_tracer file of the tracing system
@ -36,16 +40,16 @@ Write the ASCII text "hwlat" into the current_tracer file of the tracing system
redefine the threshold in microseconds (us) above which latency spikes will redefine the threshold in microseconds (us) above which latency spikes will
be taken into account. be taken into account.
Example: Example::
# echo hwlat > /sys/kernel/tracing/current_tracer # echo hwlat > /sys/kernel/tracing/current_tracer
# echo 100 > /sys/kernel/tracing/tracing_thresh # echo 100 > /sys/kernel/tracing/tracing_thresh
The /sys/kernel/tracing/hwlat_detector interface contains the following files: The /sys/kernel/tracing/hwlat_detector interface contains the following files:
width - time period to sample with CPUs held (usecs) - width - time period to sample with CPUs held (usecs)
must be less than the total window size (enforced) must be less than the total window size (enforced)
window - total period of sampling, width being inside (usecs) - window - total period of sampling, width being inside (usecs)
By default the width is set to 500,000 and window to 1,000,000, meaning that By default the width is set to 500,000 and window to 1,000,000, meaning that
for every 1,000,000 usecs (1s) the hwlat detector will spin for 500,000 usecs for every 1,000,000 usecs (1s) the hwlat detector will spin for 500,000 usecs
@ -67,11 +71,11 @@ The following tracing directory files are used by the hwlat_detector:
in /sys/kernel/tracing: in /sys/kernel/tracing:
tracing_threshold - minimum latency value to be considered (usecs) - tracing_threshold - minimum latency value to be considered (usecs)
tracing_max_latency - maximum hardware latency actually observed (usecs) - tracing_max_latency - maximum hardware latency actually observed (usecs)
tracing_cpumask - the CPUs to move the hwlat thread across - tracing_cpumask - the CPUs to move the hwlat thread across
hwlat_detector/width - specified amount of time to spin within window (usecs) - hwlat_detector/width - specified amount of time to spin within window (usecs)
hwlat_detector/window - amount of time between (width) runs (usecs) - hwlat_detector/window - amount of time between (width) runs (usecs)
The hwlat detector's kernel thread will migrate across each CPU specified in The hwlat detector's kernel thread will migrate across each CPU specified in
tracing_cpumask between each window. To limit the migration, either modify tracing_cpumask between each window. To limit the migration, either modify

1
Documentation/trace/index.rst
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@ -18,3 +18,4 @@ Linux Tracing Technologies
events-nmi events-nmi
events-msr events-msr
mmiotrace mmiotrace
hwlat_detector