1 .TH BLKPARSE 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
63 \-\-set-mask=\fIhex-mask\fR
65 Set filter mask to \fIhex-mask\fR, see blktrace (8) for masks
70 \-\-act-mask=\fImask\fR
72 Add \fImask\fR to current filter, see blktrace (8) for masks
77 \-\-input-directory=\fIdir\fR
79 Prepend \fIdir\fR to input file names
86 Standard input read batching
93 Specifies base name for input files \-\- default is \fIdevice\fR.blktrace.\fIcpu\fR.
95 As noted above, specifying \fB\-i \-\fR runs in live mode with blktrace
96 (reading data from standard in).
101 \-\-format=\fItyp,fmt\fR
105 \-\-format\-spec=\fIfmt\fR
108 (See OUTPUT DESCRIPTION AND FORMATTING for details.)
110 The \-f form specifies a format for all events
112 The \-F form allows one to specify a format for a specific
113 event type. The single\-character \fItyp\fR field is one of the
114 action specifiers described in ACTION IDENTIFIERS.
121 When \-d is specified, this will stop messages from being output to the
122 file. (Can seriously reduce the size of the resultant file when using
123 the CFQ I/O scheduler.)
130 Hash processes by name, not by PID
135 \-\-output=\fIfile\fR
144 Do \fInot\fR produce text output, used for binary (\fB\-d\fR) only
149 \-\-dump\-binary=\fIfile\fR
163 \-\-per\-program\-stats
165 Displays data sorted by program
172 Display time deltas per IO
177 \-\-stopwatch=\fIspan\fR
179 Display traces for the \fIspan\fR specified \-\- where span can be:
181 \fIend\-time\fR \-\- Display traces from time 0 through \fIend\-time\fR (in ns)
185 \fIstart:end\-time\fR \-\- Display traces from time \fIstart\fR
186 through end\-time (in ns).
193 More verbose marginal on marginal errors
205 The following trace actions are recognised:
209 A previously issued request has been completed. The output will detail the
210 sector and size of that request, as well as the success or failure of it.
214 A request that previously resided on the block layer queue or in the i/o
215 scheduler has been sent to the driver.
219 A request is being sent to the i/o scheduler for addition to the internal queue
220 and later service by the driver. The request is fully formed at this time.
224 This notes intent to queue i/o at the given location. No real requests exists
229 The data pages attached to this \fIbio\fR are not reachable by the hardware
230 and must be bounced to a lower memory location. This causes a big slowdown in
231 i/o performance, since the data must be copied to/from kernel buffers. Usually
232 this can be fixed with using better hardware -- either a better i/o controller,
233 or a platform with an IOMMU.
236 \fBM -- back merge\fR
237 A previously inserted request exists that ends on the boundary of where this i/o
238 begins, so the i/o scheduler can merge them together.
241 \fBF -- front merge\fR
242 Same as the back merge, except this i/o ends where a previously inserted
246 \fBM -- front or back merge\fR
250 \fBG -- get request\fR
251 To send any type of request to a block device, a \fIstruct request\fR
252 container must be allocated first.
256 No available request structures were available, so the issuer has to wait for
261 When i/o is queued to a previously empty block device queue, Linux will plug the
262 queue in anticipation of future ios being added before this data is needed.
266 Some request data already queued in the device, start sending requests to the
267 driver. This may happen automatically if a timeout period has passed (see next
268 entry) or if a number of requests have been added to the queue.
271 \fBT -- unplug due to timer\fR
272 If nobody requests the i/o that was queued after plugging the queue, Linux will
273 automatically unplug it after a defined period has passed.
277 On raid or device mapper setups, an incoming i/o may straddle a device or
278 internal zone and needs to be chopped up into smaller pieces for service. This
279 may indicate a performance problem due to a bad setup of that raid/dm device,
280 but may also just be part of normal boundary conditions. dm is notably bad at
281 this and will clone lots of i/o.
285 For stacked devices, incoming i/o is remapped to device below it in the i/o
286 stack. The remap action details what exactly is being remapped to what.
291 .SH "OUTPUT DESCRIPTION AND FORMATTING"
293 The output from blkparse can be tailored for specific use -- in particular, to ease
294 parsing of output, and/or limit output fields to those the user wants to see. The
295 data for fields which can be output include:
298 Action, a (small) string (1 or 2 characters) -- see table below for more details
307 RWBS field, a (small) string (1-3 characters) -- see section below for more details
310 7-character string containing the major and minor numbers of
311 the event's device (separated by a comma).
317 Minor number of event's device.
320 Major number of event's device.
332 Display packet data \-\- series of hexadecimal values
341 Time stamp (nanoseconds)
347 Elapsed value in microseconds (\fI\-t\fR command line option)
350 Payload unsigned integer
353 Note that the user can optionally specify field display width, and optionally a
354 left-aligned specifier. These precede field specifiers, with a '%' character,
355 followed by the optional left-alignment specifier (\-) followed by the width (a
356 decimal number) and then the field.
358 Thus, to specify the command in a 12-character field that is left aligned:
363 .SH "ACTION IDENTIFIERS"
365 The following table shows the various actions which may be output:
368 IO was remapped to a different device
380 IO front merged with request on queue
386 IO inserted onto request queue
389 IO back merged with request on queue
395 IO handled by request queue code
401 Unplug due to timeout
410 .SH "RWBS DESCRIPTION"
412 This is a small string containing at least one character ('R' for read, 'W'
413 for write, or 'D' for block discard operation), and optionally either
414 a 'B' (for barrier operations) or 'S' (for synchronous operations).
419 The standard header (or initial fields displayed) include:
421 "%D %2c %8s %5T.%9t %5p %2a %3d"
426 Displays the event's device major/minor as: %3d,%\-3d.
429 CPU ID (2-character field).
435 5-character field for the seconds portion of the time stamp and a 9-character field for the nanoseconds in the time stamp.
438 5-character field for the process ID.
441 2-character field for one of the actions.
444 3-character field for the RWBS data.
446 Seeing this in action:
448 8,0 3 1 0.000000000 697 G W 223490 + 8 [kjournald]
450 The header is the data in this line up to the 223490 (starting block).
451 The default output for all event types includes this header.
455 .SH "DEFAULT OUTPUT PER ACTION"
457 \fBC \-\- complete\fR
459 If a payload is present, this is presented between
460 parenthesis following the header, followed by the error value.
462 If no payload is present, the sector and number of blocks are presented
463 (with an intervening plus (+) character). If the \fB\-t\fR option
464 was specified, then the elapsed time is presented. In either case,
465 it is followed by the error value for the completion.
472 \fBI \-\- inserted\fR
476 If a payload is present, the number of payload bytes
477 is output, followed by the payload in hexadecimal between parenthesis.
479 If no payload is present, the sector and number of blocks are presented
480 (with an intervening plus (+) character). If the \fB\-t\fR option was
481 specified, then the elapsed time is presented (in parenthesis). In
482 either case, it is followed by the command associated with the event
483 (surrounded by square brackets).
486 \fBF \-\- front merge\fR
488 \fBG \-\- get request\fR
490 \fBM \-\- back merge\fR
494 The starting sector and number of blocks is output
495 (with an intervening plus (+) character), followed by the command
496 associated with the event (surrounded by square brackets).
501 The command associated with the event (surrounded by
502 square brackets) is output.
507 \fBT \-\- unplug due to timer\fR
509 The command associated with the event
510 (surrounded by square brackets) is output, followed by the number of
511 requests outstanding.
516 The original starting sector followed by the new
517 sector (separated by a slash (/) is output, followed by the command
518 associated with the event (surrounded by square brackets).
523 Sector and length is output, along with the original
524 device and sector offset.
529 To trace the i/o on the device \fI/dev/sda\fB and parse the output to human
530 readable form, use the following command:
532 % blktrace \-d /dev/sda \-o \- | blkparse \-i \-
534 (see \fIblktrace\fR (8) for more information).
535 This same behaviour can be achieve with the convenience script \fIbtrace\fR.
540 has exactly the same effect as the previous command. See \fIbtrace\fR (8) for
543 To trace the i/o on a device and save the output for later processing with
544 \fIblkparse\fR, use \fIblktrace\fR like this:
546 % blktrace /dev/sda /dev/sdb
548 This will trace i/o on the devices \fI/dev/sda\fR and \fI/dev/sdb\fR and save
549 the recorded information in the files \fIsda\fR and \fIsdb\fR in the current
550 directory, for the two different devices, respectively. This trace
551 information can later be parsed by the \fIblkparse\fR utility:
555 which will output the previously recorded tracing information in human
556 readable form to stdout.
560 \fIblkparse\fR was written by Jens Axboe, Alan D. Brunelle and Nathan Scott. This
561 man page was created from the \fIblktrace\fR documentation by Bas Zoetekouw.
565 Report bugs to <linux\-btrace@vger.kernel.org>
568 Copyright \(co 2006 Jens Axboe, Alan D. Brunelle and Nathan Scott.
570 This is free software. You may redistribute copies of it under the terms of
571 the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
572 There is NO WARRANTY, to the extent permitted by law.
574 This manual page was created for Debian by Bas Zoetekouw. It was derived from
575 the documentation provided by the authors and it may be used, distributed and
576 modified under the terms of the GNU General Public License, version 2.
578 On Debian systems, the text of the GNU General Public License can be found in
579 /usr/share/common\-licenses/GPL\-2.
582 btrace (8), blktrace (8), verify_blkparse (1), blkrawverify (1), btt (1)