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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHORS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON |
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BTREPLAY(8) BTREPLAY(8)
btreplay - recreate IO loads recorded by blktrace
btreplay [ 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.
-c <num>
--cpus=<num>
Set number of CPUs to use.
-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 (.).
-F
--find-records
Find record files automatically This option instructs
btreplay to go find all the record files in the directory
specified (either via the -d option, or in the default
directory (.).
-h
--help
Show help and exit.
-i <basename>
--input-base=<basename>
Set base name for input files. Each input 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.
-I <num>
--iterations=<num>
Set number of iterations to run. This option requires a
single parameter which specifies the number of times to run
through the input files. The default value is 1
-M <filename>
--map-devs=<filename>
Specify device mappings. This option requires a single
parameter which specifies the name of a file contain device
mappings. The file must be very simply managed, with just
two pieces of data per line:
-
The device name on the recorded system (with the
'/dev/'
removed). Example: /dev/sda would just be sda.
-
The device name on the replay system to use (again,
without the
'/dev/' path prepended).
An example file for when one would map devices /dev/sda and
/dev/sdb on the recorded system to dev/sdg and sdh on the
replay system would be:
sda sdg
sdb sdh
The only entries in the file that are allowed are these two
element lines — we do not (yet?) support the notion of
blank lines, or comment lines, or the like.
The utility allows for multiple -M options to be supplied
on the command line.
-N
--no-stalls
Disable pre-bunch stalls. When specified on the command
line, all pre-bunch stall indicators will be ignored. IOs
will be replayed without inter-bunch delays.
-x <factor>
--acc-factor=<factor>
Specify acceleration factor. Default value is 1 (no
acceleration).
-v
--verbose
Enable verbose output. When specified on the command line,
this option instructs btreplay to store information
concerning each stall and IO operation performed by
btreplay. The name of each file so created will be the
input file name used with an extension of .rep appended
onto it. Thus, an input file of the name sdab.replay.3
would generate a verbose output file with the name
sdab.replay.3.rep in the directory specified for input
files.
In addition, btreplay will also output to stderr the names
of the input files being processed.
-V
--version
Show version number and exit.
-W
--write-enable
Enable writing during replay. As a precautionary measure,
by default btreplay will not process write requests. In
order to enable btreplay to actually write to devices one
must explicitly specify the -W option.
btreplay 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), btrecord(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 BTREPLAY(8)
Pages that refer to this page: btrecord(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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