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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHORS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON |
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BTT(1) BTT(1)
btt - analyse block i/o traces produces by blktrace
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 <output name> | --seeks-per-second=<output name> ]
[ -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 ]
[ -X | --easy-parse-avgs ]
[ -z <output name> | --q2d-latencies=<output name> ]
[ -Z | --do-active ]
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.
-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 <output name>
--seeks-per-second=<output name>
Trigger btt to output seeks-per-second information. The first
column will contain a time value (seconds), and the second
column will indicate the number of seeks per second at that
point.
-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.
-X
--easy-parse-avgs
Provide data in an easy-to-parse form and write it to a file
with .avg exentsion
-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.
-Z
--do-active
The -Z will output files containing data which can be plotted
showing per-device (and total system) I/O activity.
btt was written by Alan D. Brunelle. This man page was created
from the blktrace documentation by Bas Zoetekouw.
Report bugs to <linux-btrace@vger.kernel.org>
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.
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)
This page is part of the blktrace (Linux block layer I/O tracer)
project. Information about the project can be found at [unknown
-- if you know, please contact man-pages@man7.org] It is not known
how to report bugs for this man page; if you know, please send a
mail to man-pages@man7.org. This page was obtained from the
project's upstream Git repository
⟨https://git.kernel.org/pub/scm/linux/kernel/git/axboe/blktrace.git⟩
on 2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-03-20.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
blktrace git-20070910192508 September 29, 2007 BTT(1)
Pages that refer to this page: blkparse(1), blkrawverify(1), bno_plot(1), btt(1), verify_blkparse(1), blkiomon(8), blktrace(8), btrace(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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