When specified on the command line, this directs btt to calculate seek distances based solely upon the ending block address of one IO, and the start of the next. By default btt uses the concept of the closeness to either the beginning or end of the previous IO. See the Users Manual for more details about seek distances.

Normally btt will not print out verbose information concerning per-process and per-device data. If you desire that level of detail you can specify this option.

This option will output absolute block numbers to three files prefixed by the specified output name:

prefix_device_r.dat

All read block numbers are output, first column is time (seconds), second is the block number, and the third column is the ending block number.

prefix_device_w.dat

All write block numbers are output, first column is time (seconds), second is the block number, and the third column is the ending block number.

prefix_device_c.dat

All block numbers (read and write) are output, first column is time (seconds), second is the block number, and the third column is the ending block number.

btt outputs a file containing Q and C activity, the notion of active traces simply means that there are Q or C traces occurring within a certain period of each other. The default values is 0.1 seconds; with this option allowing one to change that granularity. The smaller the value, the more data points provided.

Normally, btt will produce data for all devices detected in the traces parsed. With this option, one can reduce the analysis to one or more devices provided in the string passed to this option. The device identifiers are the major and minor number of each device, and each device identifier is separated by a colon (:). A valid specifier for devices 8,0 and 8,8 would then be: 8,0:8,8.

The -e option supplies the list of executables that will have I/Os analysed.

Shows a short summary of possible command line option

Specifies the input file to analyse. This should be a trace file produced by blktrace (8).

The -I option directs btt to output iostat-like data to the specified file. Refer to the iostat (sysstat) documentation for details on the data columns.

The -l option allows one to output per-IO D2C latencies respectively. The supplied argument provides the basis for the output name for each device.

The -L option allows one to output periodic latency information for both Q2C and D2C latencies. The frequency specified will regulate how often an average latency is output -- a floating point value expressing seconds.

The -M option takes in a file generated by the provided script (gen_disk_info.py), and allows for better output of device names.

Specifies the output file name.

The -p option will generate a file that contains a list of all IO "sequences" - showing the parts of each IO (Q, A, I/M, D, & C).

The -P option will generate a file that contains a list of all IO "sequences" - showing only the Q, D & C operation times. The D & C time values are separated from the Q time values with a vertical bar.

The -q option allows one to output per-IO Q2C latencies respectively. The supplied argument provides the basis for the output name for each device.

The -Q option allows one to output data files showing the time stamp and the depth of active commands (those issued but not completed).

Ignore remap traces; older kernels did not implement the full remap PDU.

The -s option instructs btt to output seek data, the argument provided is the basis for file names output. There are two files per device, read seeks and write seeks.

The -S option specifies the interval to use between data output, it defaults to once per second.

The -t/-T options allow one to set a start and/or end time for analysing - analysing will only be done for traces after -t's argument and before -T's argument. (-t and -T are optional, so if you specify just -t, analysis will occur for all traces after the time specified. Similarly, if only -T is specified, analysis stops after -T's seconds.)

This option instructs btt to generate a data file containing histogram information for unplug traces on a per device basis. It shows how many times an unplug was hit with a specified number of IOs released. There are 21 output values into the file, as follows:

Shows the version of btt.

Requests a more verbose output.

The -z option allows one to output per-IO Q2D latencies respectively. The supplied argument provides the basis for the output name for each device.