Usage: blktrace 

-d <dev>             | --dev=<dev>
[ -r <debugfs path>  | --relay=<debugfs path> ]
[ -o <file>          | --output=<file>]
[ -D <dir>           | --output-dir=<dir>
[ -w <time>          | --stopwatch=<time>]
[ -a <action field>  | --act-mask=<action field>]
[ -A <action mask>   | --set-mask=<action mask>]
[ -b <size>          | --buffer-size]
[ -n <number>        | --num-sub-buffers=<number>]
[ -l                 | --listen]
[ -h <hostname>      | --host=<hostname>]
[ -p <port number>   | --port=<port number>]
[ -s                 | --no-sendfile]
[ -I <devs file>     | --input-devs=<devs file>]
[ -v <version>       | --version]
[ -V <version>       | --version]
	-d Use specified device. May also be given last after options
	-r Path to mounted debugfs, defaults to /sys/kernel/debug
	-o File(s) to send output to
	-D Directory to prepend to output file names
	-w Stop after defined time, in seconds
	-a Only trace specified actions. See documentation
	-A Give trace mask as a single value. See documentation
	-b Sub buffer size in KiB (default 512)
	-n Number of sub buffers (default 4)
	-l Run in network listen mode (blktrace server)
	-h Run in network client mode, connecting to the given host
	-p Network port to use (default 8462)
	-s Make the network client NOT use sendfile() to transfer data
	-I Add devices found in <devs file>
	-v Print program version info
	-V Print program version info