Provided by: blktrace_1.2.0-5_amd64 
NAME
blkparse - produce formatted output of event streams of block devices
SYNOPSIS
blkparse [ options ]
DESCRIPTION
The blkparse utility will attempt to combine streams of events for various devices on various CPUs, and
produce a formatted output of the event information. Specifically, it will take the (machine-readable)
output of the blktrace utility and convert it to a nicely formatted and human-readable form.
As with blktrace, some details concerning blkparse will help in understanding the command line options
presented below.
- By default, blkparse expects to run in a post-processing mode; one where the trace events have been
saved by a previous run of blktrace, and blkparse is combining event streams and dumping formatted
data.
blkparse may be run in a live manner concurrently with blktrace by specifying -i - to blkparse, and
combining it with the live option for blktrace. An example would be:
% blktrace -d /dev/sda -o - | blkparse -i -
- You can set how many blkparse batches event reads via the -b option, the default is to handle events in
batches of 512.
- If you have saved event traces in blktrace with different output names (via the -o option to blktrace),
you must specify the same input name via the -i option.
- The format of the output data can be controlled via the -f or -F options -- see OUTPUT DESCRIPTION AND
FORMATTING for details.
By default, blkparse sends formatted data to standard output. This may be changed via the -o option, or
text output can be disabled via the -O option. A merged binary stream can be produced using the -d
option.
OPTIONS
-A hex-mask
--set-mask=hex-mask
Set filter mask to hex-mask, see blktrace (8) for masks
-a mask
--act-mask=mask
Add mask to current filter, see blktrace (8) for masks
-D dir
--input-directory=dir
Prepend dir to input file names
-b batch
--batch={batch}
Standard input read batching
-i file
--input=file
Specifies base name for input files -- default is device.blktrace.cpu.
As noted above, specifying -i - runs in live mode with blktrace (reading data from standard in).
-F typ,fmt
--format=typ,fmt
-f fmt
--format-spec=fmt
Sets output format (See OUTPUT DESCRIPTION AND FORMATTING for details.)
The -f form specifies a format for all events
The -F form allows one to specify a format for a specific event type. The single-character typ
field is one of the action specifiers described in ACTION IDENTIFIERS.
-M
--no-msgs
When -d is specified, this will stop messages from being output to the file. (Can seriously reduce
the size of the resultant file when using the CFQ I/O scheduler.)
-h
--hash-by-name
Hash processes by name, not by PID
-o file
--output=file
Output file
-O
--no-text-output
Do not produce text output, used for binary (-d) only
-d file
--dump-binary=file
Binary output file
-q
--quiet
Quiet mode
-s
--per-program-stats
Displays data sorted by program
-t
--track-ios
Display time deltas per IO
-w span
--stopwatch=span
Display traces for the span specified -- where span can be:
end-time -- Display traces from time 0 through end-time (in ns)
or
start:end-time -- Display traces from time start through end-time (in ns).
-v
--verbose
More verbose marginal on marginal errors
-V
--version
Display version
TRACE ACTIONS
The following trace actions are recognised:
C -- complete A previously issued request has been completed. The output will detail the sector and size
of that request, as well as the success or failure of it.
D -- issued A request that previously resided on the block layer queue or in the i/o scheduler has been
sent to the driver.
I -- inserted A request is being sent to the i/o scheduler for addition to the internal queue and later
service by the driver. The request is fully formed at this time.
Q -- queued This notes intent to queue i/o at the given location. No real requests exists yet.
B -- bounced The data pages attached to this bio are not reachable by the hardware and must be bounced to
a lower memory location. This causes a big slowdown in i/o performance, since the data must be copied
to/from kernel buffers. Usually this can be fixed with using better hardware -- either a better i/o
controller, or a platform with an IOMMU.
M -- back merge A previously inserted request exists that ends on the boundary of where this i/o begins,
so the i/o scheduler can merge them together.
F -- front merge Same as the back merge, except this i/o ends where a previously inserted requests
starts.
M -- front or back merge One of the above
M -- front or back merge One of the above.
G -- get request To send any type of request to a block device, a struct request container must be
allocated first.
S -- sleep No available request structures were available, so the issuer has to wait for one to be freed.
P -- plug When i/o is queued to a previously empty block device queue, Linux will plug the queue in
anticipation of future ios being added before this data is needed.
U -- unplug Some request data already queued in the device, start sending requests to the driver. This
may happen automatically if a timeout period has passed (see next entry) or if a number of requests
have been added to the queue.
T -- unplug due to timer If nobody requests the i/o that was queued after plugging the queue, Linux will
automatically unplug it after a defined period has passed.
X -- split On raid or device mapper setups, an incoming i/o may straddle a device or internal zone and
needs to be chopped up into smaller pieces for service. This may indicate a performance problem due
to a bad setup of that raid/dm device, but may also just be part of normal boundary conditions. dm is
notably bad at this and will clone lots of i/o.
A -- remap For stacked devices, incoming i/o is remapped to device below it in the i/o stack. The remap
action details what exactly is being remapped to what.
OUTPUT DESCRIPTION AND FORMATTING
The output from blkparse can be tailored for specific use -- in particular, to ease parsing of output,
and/or limit output fields to those the user wants to see. The data for fields which can be output
include:
a Action, a (small) string (1 or 2 characters) -- see table below for more details
c CPU id
C Command
d RWBS field, a (small) string (1-3 characters) -- see section below for more details
D 7-character string containing the major and minor numbers of the event's device (separated by a
comma).
e Error value
m Minor number of event's device.
M Major number of event's device.
n Number of blocks
N Number of bytes
p Process ID
P Display packet data -- series of hexadecimal values
s Sequence numbers
S Sector number
t Time stamp (nanoseconds)
T Time stamp (seconds)
u Elapsed value in microseconds (-t command line option)
U Payload unsigned integer
Note that the user can optionally specify field display width, and optionally a left-aligned specifier.
These precede field specifiers, with a '%' character, followed by the optional left-alignment specifier
(-) followed by the width (a decimal number) and then the field.
Thus, to specify the command in a 12-character field that is left aligned:
-f "%-12C"
ACTION IDENTIFIERS
The following table shows the various actions which may be output:
A IO was remapped to a different device
B IO bounced
C IO completion
D IO issued to driver
F IO front merged with request on queue
G Get request
I IO inserted onto request queue
M IO back merged with request on queue
P Plug request
Q IO handled by request queue code
S Sleep request
T Unplug due to timeout
U Unplug request
X Split
RWBS DESCRIPTION
This is a small string containing at least one character ('R' for read, 'W' for write, or 'D' for block
discard operation), and optionally either a 'B' (for barrier operations) or 'S' (for synchronous
operations).
DEFAULT OUTPUT
The standard header (or initial fields displayed) include:
"%D %2c %8s %5T.%9t %5p %2a %3d"
Breaking this down:
%D Displays the event's device major/minor as: %3d,%-3d.
%2c CPU ID (2-character field).
%8s Sequence number
%5T.%9t
5-character field for the seconds portion of the time stamp and a 9-character field for the
nanoseconds in the time stamp.
%5p 5-character field for the process ID.
%2a 2-character field for one of the actions.
%3d 3-character field for the RWBS data.
Seeing this in action:
8,0 3 1 0.000000000 697 G W 223490 + 8 [kjournald]
The header is the data in this line up to the 223490 (starting block). The default output for all
event types includes this header.
DEFAULT OUTPUT PER ACTION
C -- complete
If a payload is present, this is presented between parenthesis following the header, followed by the
error value.
If no payload is present, the sector and number of blocks are presented (with an intervening plus (+)
character). If the -t option was specified, then the elapsed time is presented. In either case, it is
followed by the error value for the completion.
B -- bounced
D -- issued
I -- inserted
Q -- queued
If a payload is present, the number of payload bytes is output, followed by the payload in
hexadecimal between parenthesis.
If no payload is present, the sector and number of blocks are presented (with an intervening plus (+)
character). If the -t option was specified, then the elapsed time is presented (in parenthesis). In
either case, it is followed by the command associated with the event (surrounded by square brackets).
F -- front merge
G -- get request
M -- back merge
S -- sleep
The starting sector and number of blocks is output (with an intervening plus (+) character), followed
by the command associated with the event (surrounded by square brackets).
P -- plug
The command associated with the event (surrounded by square brackets) is output.
U -- unplug
T -- unplug due to timer
The command associated with the event (surrounded by square brackets) is output, followed by the
number of requests outstanding.
X -- split
The original starting sector followed by the new sector (separated by a slash (/) is output, followed
by the command associated with the event (surrounded by square brackets).
A -- remap
Sector and length is output, along with the original device and sector offset.
EXAMPLES
To trace the i/o on the device /dev/sda and parse the output to human readable form, use the following
command:
% blktrace -d /dev/sda -o - | blkparse -i -
(see blktrace (8) for more information). This same behaviour can be achieve with the convenience script
btrace. The command
% btrace /dev/sda
has exactly the same effect as the previous command. See btrace (8) for more information.
To trace the i/o on a device and save the output for later processing with blkparse, use blktrace like
this:
% blktrace /dev/sda /dev/sdb
This will trace i/o on the devices /dev/sda and /dev/sdb and save the recorded information in the files
sda and sdb in the current directory, for the two different devices, respectively. This trace
information can later be parsed by the blkparse utility:
% blkparse sda sdb
which will output the previously recorded tracing information in human readable form to stdout.
AUTHORS
blkparse was written by Jens Axboe, Alan D. Brunelle and Nathan Scott. This man page was created from
the blktrace documentation by Bas Zoetekouw.
REPORTING BUGS
Report bugs to <linux-btrace@vger.kernel.org>
COPYRIGHT
Copyright © 2006 Jens Axboe, Alan D. Brunelle and Nathan Scott.
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.
SEE ALSO
btrace (8), blktrace (8), verify_blkparse (1), blkrawverify (1), btt (1)