From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <d43d860f1c84bd4a71dada98076fa2d4@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] trace.c
From: Peter Bosch <pb@research.bell-labs.com>
In-Reply-To: <97ec848e6375883f7a411b0a78fb3a50@plan9.ucalgary.ca>
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Date: Tue, 27 Jan 2004 14:58:52 -0500
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> trace.c came with the Jan 22 pull, but what is it?  it does show
> somewhat interesting pictures and tells me how much certain processes
> have been using the CPU, but without a man page the mind boggles :)

trace shows the kernel scheduling actions and when interrupts
occur.  it reads scheduling events from /proc/trace (unfortunately
binary format only).  the definition of a trace event can be found
in /sys/include/trace.h.

to switch on tracing:

	echo traceon > /proc/<pid>/ctl

to switch it off again:

	echo traceoff > /proc/<pid>/ctl

when real-time processes are used it also shows you the release
times and deadlines of processes.

'q'	quits trace
'+'	zooms in
'-'	zooms out
'p'	pauses trace

(hmm, i guess the above _is_ the man page ;-)).


peter.