trace doc: convert trace/hwlat_detector.txt to rst fromat
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>
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Introduction:
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=========================
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Hardware Latency Detector
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=========================
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Introduction
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-------------
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The tracer hwlat_detector is a special purpose tracer that is used to
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@ -28,7 +32,7 @@ Note that the hwlat detector should *NEVER* be used in a production environment.
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It is intended to be run manually to determine if the hardware platform has a
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problem with long system firmware service routines.
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Usage:
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Usage
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------
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Write the ASCII text "hwlat" into the current_tracer file of the tracing system
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@ -36,16 +40,16 @@ Write the ASCII text "hwlat" into the current_tracer file of the tracing system
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redefine the threshold in microseconds (us) above which latency spikes will
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be taken into account.
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Example:
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Example::
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# echo hwlat > /sys/kernel/tracing/current_tracer
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# echo 100 > /sys/kernel/tracing/tracing_thresh
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The /sys/kernel/tracing/hwlat_detector interface contains the following files:
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width - time period to sample with CPUs held (usecs)
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must be less than the total window size (enforced)
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window - total period of sampling, width being inside (usecs)
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- width - time period to sample with CPUs held (usecs)
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must be less than the total window size (enforced)
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- window - total period of sampling, width being inside (usecs)
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By default the width is set to 500,000 and window to 1,000,000, meaning that
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for every 1,000,000 usecs (1s) the hwlat detector will spin for 500,000 usecs
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@ -67,11 +71,11 @@ The following tracing directory files are used by the hwlat_detector:
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in /sys/kernel/tracing:
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tracing_threshold - minimum latency value to be considered (usecs)
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tracing_max_latency - maximum hardware latency actually observed (usecs)
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tracing_cpumask - the CPUs to move the hwlat thread across
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hwlat_detector/width - specified amount of time to spin within window (usecs)
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hwlat_detector/window - amount of time between (width) runs (usecs)
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- tracing_threshold - minimum latency value to be considered (usecs)
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- tracing_max_latency - maximum hardware latency actually observed (usecs)
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- tracing_cpumask - the CPUs to move the hwlat thread across
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- hwlat_detector/width - specified amount of time to spin within window (usecs)
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- hwlat_detector/window - amount of time between (width) runs (usecs)
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The hwlat detector's kernel thread will migrate across each CPU specified in
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tracing_cpumask between each window. To limit the migration, either modify
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@ -18,3 +18,4 @@ Linux Tracing Technologies
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events-nmi
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events-msr
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mmiotrace
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hwlat_detector
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