NAME
btt - analyse block i/o traces produces by blktrace
SYNOPSIS
btt
[ -a | --seek-absolute ]
[ -A | --all-data ]
[ -B <output name> | --dump-blocknos=<output name> ]
[ -d <seconds> | --range-delta=<seconds> ]
[ -D <dev;...> | --devices=<dev;...> ]
[ -e <exe,...> | --exes=<exe,...> ]
[ -h | --help ]
[ -i <input name> | --input-file=<input name> ]
[ -I <output name> | --iostat=<output name> ]
[ -l <output name> | --d2c-latencies=<output name> ]
[ -L <freq> | --periodic-latencies=<freq> ]
[ -M <dev map> | --dev-maps=<dev map>
[ -o <output name> | --output-file=<output name> ]
[ -p <output name> | --per-io-dump=<output name> ]
[ -P <output name> | --per-io-trees=<output name> ]
[ -q <output name> | --q2c-latencies=<output name> ]
[ -Q <output name> | --active-queue-depth=<output name> ]
[ -r | --no-remaps ]
[ -s <output name> | --seeks=<output name> ]
[ -S <interval> | --iostat-interval=<interval> ]
[ -t <sec> | --time-start=<sec> ]
[ -T <sec> | --time-end=<sec> ]
[ -u <output name> | --unplug-hist=<output name> ]
[ -v | --verbose ]
[ -V | --version ]
[ -z <output name> | --q2d-latencies=<output name> ]
DESCRIPTION
btt is a post-processing tool for the block layer IO tracing tool
called blktrace(8). As noted in its documentation, blktrace is a block
layer IO tracing mechanism which provides detailed information about
request queue operations up to user space.
btt will take in binary dump data from blkparse, and analyse the
events, producing a series of output from the analysis. It will also
build .dat files containing "range data" -- showing things like Q
activity (periods of time while Q events are being produced), C
activity (likewise for command completions), and etc.
Included with the distribution is a simple 3D plotting utility,
bno_plot, which can plot the block numbers btt outputs if the -B option
is specified. The display will display each IO generated, with the time
(seconds) along the X-axis, the block number (start) along the Y-axis
and the number of blocks transferred in the IO represented along the Z-
axis.
OPTIONS
-a
--seek-absolute
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.
-A
--all-data
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.
-B <output name>
--dump-blocknos=<output name>
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.
-d <seconds>
--range-delta=<seconds>
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.
-D <dev;...>
--devices=<dev;...>
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.
-e <exe,...>
--exes=<exe,...>
The -e option supplies the list of executables that will have I/Os
analysed.
-h
--help
Shows a short summary of possible command line option
-i <input name>
--input-file <input file>
Specifies the input file to analyse. This should be a trace file
produced by blktrace (8).
-I <output name>
--iostat=<output name>
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.
-l <output name>
--d2c-latencies=<output name>
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.
-L <freq>
--periodic-latencies=<freq>
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.
-M <dev map>
--dev-maps=<dev map>
The -M option takes in a file generated by the provided script
(gen_disk_info.py), and allows for better output of device names.
-o <output name>
--output-file=<output name>
Specifies the output file name.
-p <output name>
--per-io-dump=<output 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).
-P <output name>
--per-io-trees=<output name>
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.
-q <output name>
--q2c-latencies=<output name>
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.
-Q <output name>
--active-queue-depth=<output name>
The -Q option allows one to output data files showing the time
stamp and the depth of active commands (those issued but not
completed).
-r
--no-remaps
Ignore remap traces; older kernels did not implement the full remap
PDU.
-s <output name>
--seeks=<output name>
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.
-S <interval>
--iostat-interval=<interval>
The -S option specifies the interval to use between data output, it
defaults to once per second.
-t <sec>
--time-start=<sec>
-T <sec>
--time-end=<sec>
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.)
-u <output name>
--unplug-hist=<output name>
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:
a value of 0 represents 0..4 counts
a value of 1 represents 5..9 counts
a value of 2 represents 10..14 counts
etc, until
a value of 20 represents 100+ counts
The file name(s) generated use the text string passed as an
argument for the prefix, followed by the device identifier in
major,minor form, with a .dat extension. For example, with -u
up_hist specified on the command line: up_hist_008,032.dat.
-V
--version
Shows the version of btt.
-v
--verbose
Requests a more verbose output.
-z <output name>
--q2d-latencies=<output name>
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.
AUTHORS
btt was written by Alan D. Brunelle. This man page was created from
the blktrace documentation by Bas Zoetekouw.
REPORTING BUGS
Report bugs to <linux-btrace@vger.kernel.org>
COPYRIGHT
Copyright © 2006 Jens Axboe, Alan D. Brunelle and Nathan Scott.
This is free software. You may redistribute copies of it under the
terms of the GNU General Public License
<http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the
extent permitted by law.
This manual page was created for Debian by Bas Zoetekouw. It was
derived from the documentation provided by the authors and it may be
used, distributed and modified under the terms of the GNU General
Public License, version 2.
On Debian systems, the text of the GNU General Public License can be
found in /usr/share/common-licenses/GPL-2.
SEE ALSO
The btt Users Guide, which can be found in
/usr/share/doc/blktrace/btt.pdf
bno_plot (1), blktrace (8), blkparse (1), verify_blkparse (1),
blkrawverify (1), btt (1)