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trace doc: convert trace/events-nmi.txt to rst format 

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 13:39:45 +08:00 committed by Jonathan Corbet
parent 47e073d2ad
commit 15ba053871
3 changed files with 46 additions and 43 deletions
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45
Documentation/trace/events-nmi.rst Normal file
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================
NMI Trace Events
================
These events normally show up here:
/sys/kernel/debug/tracing/events/nmi
nmi_handler
-----------
You might want to use this tracepoint if you suspect that your
NMI handlers are hogging large amounts of CPU time. The kernel
will warn if it sees long-running handlers::
INFO: NMI handler took too long to run: 9.207 msecs
and this tracepoint will allow you to drill down and get some
more details.
Let's say you suspect that perf_event_nmi_handler() is causing
you some problems and you only want to trace that handler
specifically. You need to find its address::
$ grep perf_event_nmi_handler /proc/kallsyms
ffffffff81625600 t perf_event_nmi_handler
Let's also say you are only interested in when that function is
really hogging a lot of CPU time, like a millisecond at a time.
Note that the kernel's output is in milliseconds, but the input
to the filter is in nanoseconds! You can filter on 'delta_ns'::
cd /sys/kernel/debug/tracing/events/nmi/nmi_handler
echo 'handler==0xffffffff81625600 && delta_ns>1000000' > filter
echo 1 > enable
Your output would then look like::
$ cat /sys/kernel/debug/tracing/trace_pipe
<idle>-0 [000] d.h3 505.397558: nmi_handler: perf_event_nmi_handler() delta_ns: 3236765 handled: 1
<idle>-0 [000] d.h3 505.805893: nmi_handler: perf_event_nmi_handler() delta_ns: 3174234 handled: 1
<idle>-0 [000] d.h3 506.158206: nmi_handler: perf_event_nmi_handler() delta_ns: 3084642 handled: 1
<idle>-0 [000] d.h3 506.334346: nmi_handler: perf_event_nmi_handler() delta_ns: 3080351 handled: 1

43
Documentation/trace/events-nmi.txt
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@ -1,43 +0,0 @@
NMI Trace Events
These events normally show up here:
/sys/kernel/debug/tracing/events/nmi
--
nmi_handler:
You might want to use this tracepoint if you suspect that your
NMI handlers are hogging large amounts of CPU time. The kernel
will warn if it sees long-running handlers:
INFO: NMI handler took too long to run: 9.207 msecs
and this tracepoint will allow you to drill down and get some
more details.
Let's say you suspect that perf_event_nmi_handler() is causing
you some problems and you only want to trace that handler
specifically. You need to find its address:
$ grep perf_event_nmi_handler /proc/kallsyms
ffffffff81625600 t perf_event_nmi_handler
Let's also say you are only interested in when that function is
really hogging a lot of CPU time, like a millisecond at a time.
Note that the kernel's output is in milliseconds, but the input
to the filter is in nanoseconds! You can filter on 'delta_ns':
cd /sys/kernel/debug/tracing/events/nmi/nmi_handler
echo 'handler==0xffffffff81625600 && delta_ns>1000000' > filter
echo 1 > enable
Your output would then look like:
$ cat /sys/kernel/debug/tracing/trace_pipe
<idle>-0 [000] d.h3 505.397558: nmi_handler: perf_event_nmi_handler() delta_ns: 3236765 handled: 1
<idle>-0 [000] d.h3 505.805893: nmi_handler: perf_event_nmi_handler() delta_ns: 3174234 handled: 1
<idle>-0 [000] d.h3 506.158206: nmi_handler: perf_event_nmi_handler() delta_ns: 3084642 handled: 1
<idle>-0 [000] d.h3 506.334346: nmi_handler: perf_event_nmi_handler() delta_ns: 3080351 handled: 1

1
Documentation/trace/index.rst
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@ -15,3 +15,4 @@ Linux Tracing Technologies
events events
events-kmem events-kmem
events-power events-power
events-nmi