1BTRECORD(8) BTRECORD(8)
2
6 btrecord - recreate IO loads recorded by blktrace
7
11 Usage:
12 btrecord [ options ] <dev...>
14
18 The btrecord and btreplay tools provide the ability to record and
19 replay IOs captured by the blktrace utility. Attempts are made to main‐
20 tain ordering, CPU mappings and time-separation of IOs.
21 The blktrace utility provides the ability to collect detailed traces
25 from the kernel for each IO processed by the block IO layer. The traces
26 provide a complete timeline for each IO processed, including detailed
27 information concerning when an IO was first received by the block IO
28 layer — indicating the device, CPU number, time stamp, IO direction,
29 sector number and IO size (number of sectors). Using this information,
30 one is able to replay the IO again on the same machine or another set
31 up entirely.
32 The basic operating work-flow to replay IOs would be something like:
35 -
38 Run blktrace to collect traces. Here you specify the
39 device or devices that you wish to trace and later replay IOs upon.
40 Note:
41 the only traces you are interested in are QUEUE requests —
42 thus, to save system resources (including storage for traces), one
43 could
44 specify the -a queue command line option to blktrace.
45 -
48 While blktrace is running, you run the workload that you
49 are interested in.
50 -
53 When the work load has completed, you stop the blktrace
54 utility (thus saving all traces over the complete workload).
55 -
58 You extract the pertinent IO information from the traces saved by
59 blktrace using the btrecord utility. This will parse
60 each trace file created by blktrace, and crafty IO descriptions
61 to be used in the next phase of the workload processing.
62 -
65 Once btrecord has successfully created a series of data
66 files to be processed, you can run the btreplay utility which
67 attempts to generate the same IOs seen during the sample workload
68 phase.
69
73 -d <dir>
74 --input-directory=<dir>
75 Set input directory. This option requires a single parameter
76 providing the directory name for where input files are to be
77 found. The default directory is the current directory (.).
78 -D <dir>
80 --output-directory=<dir>
81 Set output directory. This option requires a single parameter
82 providing the directory name for where output files are to be
83 found. The default directory is the current directory (.).
84 -F
86 --find-traces
87 Find trace files automatically This option instructs btreplay to
88 go find all the trace files in the directory specified (either
89 via the -d option, or in the default directory (.).
90 -h
92 --help
93 Show help and exit.
94 -V
96 --version
97 Show version number and exit.
98 -m <nanoseconds>
100 --max-bunch-time=<nanoseconds>
101 The -m option requires a single parameter which specifies an
102 amount of time (in nanoseconds) to include in any one bunch of
103 IOs that are to be processed. The smaller the value, the smaller
104 the number of IOs processed at one time — perhaps yielding in
105 more realistic replay. However, after a certain point the
106 amount of overhead per bunch may result in additional real
107 replay time, thus yielding less accurate replay times.
108 The default value is 10,000,000 nanoseconds (10 milliseconds).
110 -M <num>
112 --max-pkts=<num>
113 Set maximum number of packets per bunch. The -M option requires
114 a single parameter which specifies the maximum number of IOs to
115 store in a single bunch. As with the -m option, smaller values
116 may or may not yield more accurate replay times.
117 The default value is 8, with a maximum value of up to 512 being
119 supported.
120 -o <basename>
122 --output-base=<basename>
123 Set base name for output files. Each output file has 3 fields:
124 1.
126 Device identifier (taken directly from the device name of
127 the
128 blktrace output file).
129 2.
131 btrecord base name — by default ``replay''.
132 3.
134 The CPU number (again, taken directly from the
135 blktrace output file name).
136 This option requires a single parameter that will override the
138 default name (replay), and replace it with the specified value.
139 -v
141 --verbose
142 Enable verbose output. This option will output some simple sta‐
143 tistics at the end of a successful run. Example output is:
144 sdab:0: 580661 pkts (tot), 126030 pkts (replay), 89809 bunches, 1.4 pkts/bunch
146 sdab:1: 2559775 pkts (tot), 430172 pkts (replay), 293029 bunches, 1.5 pkts/bunch
147 sdab:2: 653559 pkts (tot), 136522 pkts (replay), 102288 bunches, 1.3 pkts/bunch
148 sdab:3: 474773 pkts (tot), 117849 pkts (replay), 69572 bunches, 1.7 pkts/bunch
149 The meaning of the columns is:
151 1.
153 The first field contains the device name and CPU identi‐
154 fier. Thus:
155 sdab:0: means the device sdab and traces on CPU 0.
156 2.
158 The second field contains the total number of packets pro‐
159 cessed for each
160 device file.
161 3.
163 The next field shows the number of packets eligible for
164 replay.
165 4.
167 The fourth field contains the total number of IO bunches.
168 5.
170 The last field shows the average number of IOs per bunch
171 recorded.
172
176 btrecord was written by Alan D. Brunelle. This man page was created
177 from the btreplay documentation by Bas Zoetekouw.
178
182 Report bugs to <linux-btrace@vger.kernel.org>
183
186 Copyright © 2007 Alan D. Brunelle, Alan D. Brunelle and Nathan Scott.
187 This is free software. You may redistribute copies of it under the
188 terms of the GNU General Public License
189 <http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the
190 extent permitted by law.
191 This manual page was created for Debian by Bas Zoetekouw. It was
192 derived from the documentation provided by the authors and it may be
193 used, distributed and modified under the terms of the GNU General Pub‐
194 lic License, version 2.
195 On Debian systems, the text of the GNU General Public License can be
196 found in /usr/share/common-licenses/GPL-2.
197
200 The full documentation for btreplay can be found in /usr/share/doc/blk‐
201 trace on Debian systems.
202 blktrace (8), blkparse (1), btreplay (8)
203blktrace git-20071207142532 December 8, 2007 BTRECORD(8)