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.
Device identifier (taken directly from the device name of the
blktrace output file).
btrecord base name — by default ``replay''.
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.
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.
In addition, btreplay will also output to stderr the names of the input files being processed.
btreplay was written by Alan D. Brunelle. This man page was created from the btreplay documentation by Bas Zoetekouw.
Report bugs to <email@example.com>
Copyright © 2007 Alan D. Brunelle, Alan D. Brunelle and
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)
|December 8, 2007||blktrace git-20071207142532|