1 .TH BTREPLAY 8 "December 8, 2007" "blktrace git\-20071207142532" ""
5 btreplay \- recreate IO loads recorded by blktrace
9 .B btreplay [ \fIoptions\fR ] <\fIdev\fR...>
15 The \fIbtrecord\fR and \fIbtreplay\fR tools provide the ability to
16 record and replay IOs captured by the \fIblktrace\fR utility. Attempts
17 are made to maintain ordering, CPU mappings and time-separation of IOs.
21 The \fIblktrace\fR utility provides the ability to collect detailed
22 traces from the kernel for each IO processed by the block IO layer. The
23 traces provide a complete timeline for each IO processed, including
24 detailed information concerning when an IO was first received by the block
25 IO layer \(em indicating the device, CPU number, time stamp, IO direction,
26 sector number and IO size (number of sectors). Using this information,
27 one is able to \fBreplay\fR the IO again on the same machine or another
31 The basic operating work-flow to replay IOs would be something like:
34 Run \fIblktrace\fR to collect traces. Here you specify the
35 device or devices that you wish to trace and later replay IOs upon. Note:
36 the only traces you are interested in are \fBQUEUE\fR requests \(em
37 thus, to save system resources (including storage for traces), one could
38 specify the \fI-a queue\fR command line option to \fIblktrace\fR.
41 While \fIblktrace\fR is running, you run the workload that you
45 When the work load has completed, you stop the \fIblktrace\fR
46 utility (thus saving all traces over the complete workload).
49 You extract the pertinent IO information from the traces saved by
50 \fIblktrace\fR using the \fIbtrecord\fR utility. This will parse
51 each trace file created by \fIblktrace\fR, and crafty IO descriptions
52 to be used in the next phase of the workload processing.
55 Once \fIbtrecord\fR has successfully created a series of data
56 files to be processed, you can run the \fIbtreplay\fR utility which
57 attempts to generate the same IOs seen during the sample workload phase.
66 Set number of CPUs to use.
71 \-\-input\-directory=<\fIdir\fR>
74 This option requires a single parameter providing the directory
75 name for where input files are to be found. The default directory is the
76 current directory (\fI.\fR).
83 Find record files automatically
84 This option instructs \fIbtreplay\fR to go find all the record files in the
85 directory specified (either via the \fI-d\fR option, or in the default
98 \-\-input\-base=<\fIbasename\fR>
100 Set base name for input files.
101 Each input file has 3 fields:
103 Device identifier (taken directly from the device name of the
104 \fIblktrace\fR output file).
106 \fIbtrecord\fR base name \(em by default ``replay''.
108 The CPU number (again, taken directly from the
109 \fIblktrace\fR output file name).
111 This option requires a single parameter that will override the default name
112 (replay), and replace it with the specified value.
117 \-\-iterations=<\fInum\fR>
119 Set number of iterations to run.
120 This option requires a single parameter which specifies the number of times
121 to run through the input files. The default value is 1
126 \-\-map\-devs=<\fIfilename\fR>
128 Specify device mappings.
129 This option requires a single parameter which specifies the name of a
130 file contain device mappings. The file must be very simply managed, with
131 just two pieces of data per line:
134 The device name on the recorded system (with the '\fI/dev/\fR'
135 removed). Example: \fI/dev/sda\fR would just be \fIsda\fR.
138 The device name on the replay system to use (again, without the
139 '\fI/dev/\fR' path prepended).
142 An example file for when one would map devices \fI/dev/sda\fR and
143 \fI/dev/sdb\fR on the recorded system to \fIdev/sdg\fR and
144 \fIsdh\fR on the replay system would be:
153 The only entries in the file that are allowed are these two element lines \(em
154 we do not (yet?) support the notion of blank lines, or comment lines, or the
158 The utility allows for multiple \fI-M\fR options to be
159 supplied on the command line.
166 Disable pre-bunch stalls.
167 When specified on the command line, all pre-bunch stall indicators will be
168 ignored. IOs will be replayed without inter-bunch delays.
173 \-\-acc\-factor=<\fIfactor\fR>
175 Specify acceleration factor. Default value is 1 (no acceleration).
182 Enable verbose output.
183 When specified on the command line, this option instructs \fIbtreplay\fR
184 to store information concerning each \fBstall\fR and IO operation
185 performed by \fIbtreplay\fR. The name of each file so created will be
186 the input file name used with an extension of \fI.rep\fR appended onto
187 it. Thus, an input file of the name \fIsdab.replay.3\fR would generate a
188 verbose output file with the name \fIsdab.replay.3.rep\fR in the
189 directory specified for input files.
191 In addition, \fIbtreplay\fR will also output to \fIstderr\fR the
192 names of the input files being processed.
199 Show version number and exit.
206 Enable writing during replay.
207 As a precautionary measure, by default \fIbtreplay\fR will not
208 process \fBwrite\fR requests. In order to enable \fIbtreplay\fR to
209 actually \fBwrite\fR to devices one must explicitly specify the
215 \fIbtreplay\fR was written by Alan D. Brunelle. This
216 man page was created from the \fIbtreplay\fR documentation by Bas Zoetekouw.
220 Report bugs to <linux\-btrace@vger.kernel.org>
223 Copyright \(co 2007 Alan D. Brunelle, Alan D. Brunelle and Nathan Scott.
225 This is free software. You may redistribute copies of it under the terms of
226 the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
227 There is NO WARRANTY, to the extent permitted by law.
229 This manual page was created for Debian by Bas Zoetekouw. It was derived from
230 the documentation provided by the authors and it may be used, distributed and
231 modified under the terms of the GNU General Public License, version 2.
233 On Debian systems, the text of the GNU General Public License can be found in
234 /usr/share/common\-licenses/GPL\-2.
237 The full documentation for btreplay can be found in /usr/share/doc/blktrace on Debian systems.
239 blktrace (8), blkparse (1), btrecord (8)