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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHORS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON |
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BTRECORD(8) BTRECORD(8)
btrecord - recreate IO loads recorded by blktrace
Usage:
btrecord [ options ] <dev...>
The btrecord and btreplay tools provide the ability to record and
replay IOs captured by the blktrace utility. Attempts are made to
maintain ordering, CPU mappings and time-separation of IOs.
The blktrace utility provides the ability to collect detailed
traces from the kernel for each IO processed by the block IO
layer. The traces provide a complete timeline for each IO
processed, including detailed information concerning when an IO
was first received by the block IO layer — indicating the device,
CPU number, time stamp, IO direction, sector number and IO size
(number of sectors). Using this information, one is able to replay
the IO again on the same machine or another set up entirely.
The basic operating work-flow to replay IOs would be something
like:
-
Run blktrace to collect traces. Here you specify the
device or devices that you wish to trace and later replay IOs
upon. Note:
the only traces you are interested in are QUEUE requests —
thus, to save system resources (including storage for traces),
one could
specify the -a queue command line option to blktrace.
-
While blktrace is running, you run the workload that you
are interested in.
-
When the work load has completed, you stop the blktrace
utility (thus saving all traces over the complete workload).
-
You extract the pertinent IO information from the traces saved
by
blktrace using the btrecord utility. This will parse
each trace file created by blktrace, and crafty IO
descriptions
to be used in the next phase of the workload processing.
-
Once btrecord has successfully created a series of data
files to be processed, you can run the btreplay utility which
attempts to generate the same IOs seen during the sample
workload phase.
-d <dir>
--input-directory=<dir>
Set input directory. This option requires a single
parameter providing the directory name for where input
files are to be found. The default directory is the current
directory (.).
-D <dir>
--output-directory=<dir>
Set output directory. This option requires a single
parameter providing the directory name for where output
files are to be found. The default directory is the current
directory (.).
-F
--find-traces
Find trace files automatically This option instructs
btreplay to go find all the trace files in the directory
specified (either via the -d option, or in the default
directory (.).
-h
--help
Show help and exit.
-V
--version
Show version number and exit.
-m <nanoseconds>
--max-bunch-time=<nanoseconds>
The -m option requires a single parameter which specifies
an amount of time (in nanoseconds) to include in any one
bunch of IOs that are to be processed. The smaller the
value, the smaller the number of IOs processed at one time
— perhaps yielding in more realistic replay. However,
after a certain point the amount of overhead per bunch may
result in additional real replay time, thus yielding less
accurate replay times.
The default value is 10,000,000 nanoseconds (10
milliseconds).
-M <num>
--max-pkts=<num>
Set maximum number of packets per bunch. The -M option
requires a single parameter which specifies the maximum
number of IOs to store in a single bunch. As with the -m
option, smaller values may or may not yield more accurate
replay times.
The default value is 8, with a maximum value of up to 512
being supported.
-o <basename>
--output-base=<basename>
Set base name for output files. Each output file has 3
fields:
1.
Device identifier (taken directly from the device name
of the
blktrace output file).
2.
btrecord base name — by default ``replay''.
3.
The CPU number (again, taken directly from the
blktrace output file name).
This option requires a single parameter that will override
the default name (replay), and replace it with the
specified value.
-v
--verbose
Enable verbose output. This option will output some simple
statistics at the end of a successful run. Example output
is:
sdab:0: 580661 pkts (tot), 126030 pkts (replay), 89809 bunches, 1.4 pkts/bunch
sdab:1: 2559775 pkts (tot), 430172 pkts (replay), 293029 bunches, 1.5 pkts/bunch
sdab:2: 653559 pkts (tot), 136522 pkts (replay), 102288 bunches, 1.3 pkts/bunch
sdab:3: 474773 pkts (tot), 117849 pkts (replay), 69572 bunches, 1.7 pkts/bunch
The meaning of the columns is:
1.
The first field contains the device name and CPU
identifier. Thus:
sdab:0: means the device sdab and traces on CPU 0.
2.
The second field contains the total number of packets
processed for each
device file.
3.
The next field shows the number of packets eligible
for replay.
4.
The fourth field contains the total number of IO
bunches.
5.
The last field shows the average number of IOs per
bunch recorded.
btrecord was written by Alan D. Brunelle. This man page was
created from the btreplay documentation by Bas Zoetekouw.
Report bugs to <linux-btrace@vger.kernel.org>
Copyright © 2007 Alan D. Brunelle, 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 full documentation for btreplay can be found in
/usr/share/doc/blktrace on Debian systems.
blktrace(8), blkparse(1), btreplay(8)
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-20071207142532 December 8, 2007 BTRECORD(8)
Pages that refer to this page: btreplay(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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