Block IO Tracing
----------------

Written by Jens Axboe <axboe@suse.de> (initial version and kernel support) and
Alan D. Brunelle (threading and splitup into two seperate programs).


Requirements
------------

You need to be running a 2.6.13-mm1 kernel with the blk-trace patch
included in this repository. If you forgot where you got it, the url is:

rsync://rsync.kernel.org/pub/scm/linux/kernel/git/axboe/blktrace.git


Usage
-----

% blktrace -d <dev> [-o <output> -a <trace> [-a <trace>]]
	-a <trace> is one of: (use multiple -a options to get more)
		READ
		WRITE
		BARRIER
		SYNC
		QUEUE
		REQUEUE
		ISSUE
		COMPLETE
		FS
		PC
	--- run task to generate load to be traced ---
	<SIGINT to kill>
	--- Generates:
		<output>_out.[0..ncpus] : Contains binary trace data

	% blkparse -i <input> [-o <output>]
	--- Generates:
		<output>_log.[0..ncpus] : Contains formatted trace data, if
		output logging is added with the -o option.
		Merged formatted trace data to stdout


If you want to do live tracing, you can pipe the data between blktrace
and blkparse:

% blktrace -d <device> -o - | blkparse -i -

This has a small risk of displaying some traces a little out of sync, since
it will do batch sorts of input events. Similarly, you can do traces over
the network with eg netcat:

% blktrace -d /dev/sda -o - | netcat parsehost portno
% netcat -l -p portno tracehost | blkparse -i -

Which will send the traces from tracehost to parsehost over the network on
the defined port number.


20050906, Jens Axboe <axboe@suse.de>