1 .TH BLKTPARSE 1 "March 6, 2007" "blktrace git\-20070306202522" ""
5 blkparse \- produce formatted output of event streams of block devices
9 .B blkparse [ \fIoptions\fR ]
14 The \fIblkparse\fR utility will attempt to combine streams of events for
15 various devices on various CPUs, and produce a formatted output of the event
16 information. Specifically, it will take the (machine-readable) output of the
17 \fIblktrace\fR utility and convert it to a nicely formatted and human-readable
20 As with \fIblktrace\fR, some details concerning \fIblkparse\fR
21 will help in understanding the command line options presented below.
26 By default, \fIblkparse\fR expects to run in a post-processing mode; one where
27 the trace events have been saved by a previous run of blktrace, and blkparse
28 is combining event streams and dumping formatted data.
30 blkparse may be run in a live manner concurrently with blktrace by specifying
31 \fB\-i \-\fR to blkparse, and combining it with the live option for blktrace.
34 % blktrace \-d /dev/sda \-o \- | blkparse \-i \-
38 You can set how many blkparse batches event reads via the \fB\-b\fR option, the
39 default is to handle events in batches of 512.
43 If you have saved event traces in blktrace with different output names (via
44 the \fB\-o\fR option to blktrace), you must specify the same input name via the
49 The format of the output data can be controlled via the \fB\-f\fR or \fB\-F\fR
50 options \-\- see OUTPUT DESCRIPTION AND FORMATTING for details.
53 By default, blkparse sends formatted data to standard output. This may
54 be changed via the \fB\-o\fR option, or text output can be disabled via the
55 \fB\-O\fR option. A merged binary stream can be produced using the \fB\-d\fR
66 Standard input read batching
73 Specifies base name for input files \-\- default is \fIdevice\fR.blktrace.\fIcpu\fR.
75 As noted above, specifying \fB\-i \-\fR runs in live mode with blktrace
76 (reading data from standard in).
81 \-\-format=\fItyp,fmt\fR
85 \-\-format\-spec=\fIfmt\fR
88 (See OUTPUT DESCRIPTION AND FORMATTING for details.)
90 The \-f form specifies a format for all events
92 The \-F form allows one to specify a format for a specific
93 event type. The single\-character \fItyp\fR field is one of the
94 action specifiers described in ACTION IDENTIFIERS.
101 Print missing entries
108 Hash processes by name, not by PID
113 \-\-output=\fIfile\fR
122 Do \fInot\fR produce text output, used for binary (\fB\-d\fR) only
127 \-\-dump\-binary=\fIfile\fR
141 \-\-per\-program\-stats
143 Displays data sorted by program
150 Display time deltas per IO
155 \-\-stopwatch=\fIspan\fR
157 Display traces for the \fIspan\fR specified \-\- where span can be:
159 \fIend\-time\fR \-\- Display traces from time 0 through \fIend\-time\fR (in ns)
163 \fIstart:end\-time\fR \-\- Display traces from time \fIstart\fR
164 through end\-time (in ns).
171 More verbose marginal on marginal errors
183 The following trace actions are recognised:
187 A previously issued request has been completed. The output will detail the
188 sector and size of that request, as well as the success or failure of it.
192 A request that previously resided on the block layer queue or in the i/o
193 scheduler has been sent to the driver.
197 A request is being sent to the i/o scheduler for addition to the internal queue
198 and later service by the driver. The request is fully formed at this time.
202 This notes intent to queue i/o at the given location. No real requests exists
207 The data pages attached to this \fIbio\fR are not reachable by the hardware
208 and must be bounced to a lower memory location. This causes a big slowdown in
209 i/o performance, since the data must be copied to/from kernel buffers. Usually
210 this can be fixed with using better hardware -- either a better i/o controller,
211 or a platform with an IOMMU.
214 \fBM -- back merge\fR
215 A previously inserted request exists that ends on the boundary of where this i/o
216 begins, so the i/o scheduler can merge them together.
219 \fBF -- front merge\fR
220 Same as the back merge, except this i/o ends where a previously inserted
224 \fBM --front or back merge\fR
228 \fBM -- front or back merge\fR
232 \fBG -- get request\fR
233 To send any type of request to a block device, a \fIstruct request\fR
234 container must be allocated first.
238 No available request structures were available, so the issuer has to wait for
243 When i/o is queued to a previously empty block device queue, Linux will plug the
244 queue in anticipation of future ios being added before this data is needed.
248 Some request data already queued in the device, start sending requests to the
249 driver. This may happen automatically if a timeout period has passed (see next
250 entry) or if a number of requests have been added to the queue.
253 \fBT -- unplug due to timer\fR
254 If nobody requests the i/o that was queued after plugging the queue, Linux will
255 automatically unplug it after a defined period has passed.
259 On raid or device mapper setups, an incoming i/o may straddle a device or
260 internal zone and needs to be chopped up into smaller pieces for service. This
261 may indicate a performance problem due to a bad setup of that raid/dm device,
262 but may also just be part of normal boundary conditions. dm is notably bad at
263 this and will clone lots of i/o.
267 For stacked devices, incoming i/o is remapped to device below it in the i/o
268 stack. The remap action details what exactly is being remapped to what.
273 .SH "OUTPUT DESCRIPTION AND FORMATTING"
275 The output from blkparse can be tailored for specific use -- in particular, to ease
276 parsing of output, and/or limit output fields to those the user wants to see. The
277 data for fields which can be output include:
280 Action, a (small) string (1 or 2 characters) -- see table below for more details
289 RWBS field, a (small) string (1-3 characters) -- see section below for more details
292 7-character string containing the major and minor numbers of
293 the event's device (separated by a comma).
299 Minor number of event's device.
302 Major number of event's device.
314 Display packet data \-\- series of hexadecimal values
323 Time stamp (nanoseconds)
329 Elapsed value in microseconds (\fI\-t\fR command line option)
332 Payload unsigned integer
335 Note that the user can optionally specify field display width, and optionally a
336 left-aligned specifier. These precede field specifiers, with a '%' character,
337 followed by the optional left-alignment specifier (\-) followed by the width (a
338 decimal number) and then the field.
340 Thus, to specify the command in a 12-character field that is left aligned:
345 .SH "ACTION IDENTIFIERS"
347 The following table shows the various actions which may be output:
350 IO was remapped to a different device
362 IO front merged with request on queue
368 IO inserted onto request queue
371 IO back merged with request on queue
377 IO handled by request queue code
383 Unplug due to timeout
392 .SH "RWBS DESCRIPTION"
394 This is a small string containing at least one character ('R' for read, 'W' for
395 write operation), and optionally either a 'B' (for barrier operations) or 'S' (for
396 synchronous operations).
401 The standard header (or initial fields displayed) include:
403 "%D %2c %8s %5T.%9t %5p %2a %3d"
408 Displays the event's device major/minor as: %3d,%\-3d.
411 CPU ID (2-character field).
417 5-character field for the seconds portion of the time stamp and a 9-character field for the nanoseconds in the time stamp.
420 5-character field for the process ID.
423 2-character field for one of the actions.
426 3-character field for the RWBS data.
428 Seeing this in action:
430 8,0 3 1 0.000000000 697 G W 223490 + 8 [kjournald]
432 The header is the data in this line up to the 223490 (starting block).
433 The default output for all event types includes this header.
437 .SH "DEFAULT OUTPUT PER ACTION"
439 \fBC \-\- complete\fR
441 If a payload is present, this is presented between
442 parenthesis following the header, followed by the error value.
444 If no payload is present, the sector and number of blocks are presented
445 (with an intervening plus (+) character). If the \fB\-t\fR option
446 was specified, then the elapsed time is presented. In either case,
447 it is followed by the error value for the completion.
454 \fBI \-\- inserted\fR
458 If a payload is present, the number of payload bytes
459 is output, followed by the payload in hexadecimal between parenthesis.
461 If no payload is present, the sector and number of blocks are presented
462 (with an intervening plus (+) character). If the \fB\-t\fR option was
463 specified, then the elapsed time is presented (in parenthesis). In
464 either case, it is followed by the command associated with the event
465 (surrounded by square brackets).
468 \fBF \-\- front merge\fR
470 \fBG \-\- get request\fR
472 \fBM \-\- back merge\fR
476 The starting sector and number of blocks is output
477 (with an intervening plus (+) character), followed by the command
478 associated with the event (surrounded by square brackets).
483 The command associated with the event (surrounded by
484 square brackets) is output.
489 \fBT \-\- unplug due to timer\fR
491 The command associated with the event
492 (surrounded by square brackets) is output, followed by the number of
493 requests outstanding.
498 The original starting sector followed by the new
499 sector (separated by a slash (/) is output, followed by the command
500 associated with the event (surrounded by square brackets).
505 Sector and length is output, along with the original
506 device and sector offset.
511 To trace the i/o on the device \fI/dev/hda\fB and parse the output to human
512 readable form, use the following command:
514 % blktrace \-d /dev/sda \-o \- | blkparse \-i \-
516 (see \fIblktrace\fR (8) for more information).
517 This same behaviour can be achieve with the convenience script \fIbtrace\fR.
522 has exactly the same effect as the previous command. See \fIbtrace\fR (8) for
525 To trace the i/o on a device and save the output for later processing with
526 \fIblkparse\fR, use \fIblktrace\fR like this:
528 % blktrace /dev/sda /dev/sdb
530 This will trace i/o on the devices \fI/dev/sda\fR and \fI/dev/sdb\fR and save
531 the recorded information in the files \fIsda\fR and \fIsdb\fR in the current
532 directory, for the two different devices, respectively. This trace
533 information can later be parsed by the \fIblkparse\fR utility:
537 which will output the previously recorded tracing information in human
538 readable form to stdout.
542 \fIblkparse\fR was written by Jens Axboe, Alan D. Brunelle and Nathan Scott. This
543 man page was created from the \fIblktrace\fR documentation by Bas Zoetekouw.
547 Report bugs to <linux\-btrace@vger.kernel.org>
550 Copyright \(co 2006 Jens Axboe, Alan D. Brunelle and Nathan Scott.
552 This is free software. You may redistribute copies of it under the terms of
553 the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
554 There is NO WARRANTY, to the extent permitted by law.
556 This manual page was created for Debian by Bas Zoetekouw. It was derived from
557 the documentation provided by the authors and it may be used, distributed and
558 modified under the terms of the GNU General Public License, version 2.
560 On Debian systems, the text of the GNU General Public License can be found in
561 /usr/share/common\-licenses/GPL\-2.
564 btrace (8), blktrace (8), verify_blkparse (1), blkrawverify (1), btt (1)