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

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NMI Trace Events

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These events normally show up here:

	/sys/kernel/debug/tracing/events/nmi

--

nmi_handler:

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:

will warn if it sees long-running handlers::

	INFO: NMI handler took too long to run: 9.207 msecs

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:

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':

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:

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

   events

   events-kmem

   events-power

   events-nmi