186 lines
5.1 KiB
Plaintext
186 lines
5.1 KiB
Plaintext
Block IO Tracing
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----------------
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Written by Jens Axboe <axboe@kernel.dk> (initial version and kernel support),
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Alan D. Brunelle (threading and splitup into two seperate programs),
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Nathan Scott <nathans@sgi.com> (bug fixes, process names, multiple devices)
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Also thanks to Tom Zanussi <zanussi@us.ibm.com> for good input and
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patches.
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Requirements
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------------
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blktrace was integrated into the mainline kernel between 2.6.16 and 2.6.17-rc1.
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The target trace needs to run on a kernel at least that new.
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git://git.kernel.dk/blktrace.git
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If you don't have git, you can get hourly snapshots from:
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http://brick.kernel.dk/snaps/
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The snapshots include the full git object database as well. kernel.org has
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excessively long mirror times, so if you have git installed, you can pull
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the master tree from:
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git://git.kernel.dk/blktrace.git
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For browsing the repo over http and viewing history etc, you can direct
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your browser to:
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http://git.kernel.dk/
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A blktrace visualization tool, iowatcher, was added to blktrace in version
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1.1.0. It requires librsvg and either png2theora or ffmpeg to generate movies.
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Usage
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-----
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$ blktrace -d <dev> [ -r debug_path ] [ -o output ] [ -k ] [ -w time ]
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[ -a action ] [ -A action mask ]
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-d Use specified device. May also be given last after options.
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-r Path to mounted debugfs, defaults to /sys/kernel/debug.
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-o File(s) to send output to.
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-D Directory to prepend to output file names.
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-k Kill running trace.
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-w Stop after defined time, in seconds.
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-a Only trace specific actions (use more -a options to add actions).
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Available actions are:
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READ
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WRITE
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BARRIER
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SYNC
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QUEUE
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REQUEUE
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ISSUE
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COMPLETE
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FS
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PC
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-A Give the trace mask directly as a number.
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-b Sub buffer size in KiB.
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-n Number of sub buffers.
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-l Run in network listen mode (blktrace server)
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-h Run in network client mode, connecting to the given host
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-p Network port to use (default 8462)
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-s Disable network client use of sendfile() to transfer data
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-V Print program version info.
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$ blkparse -i <input> [ -o <output> ] [ -b rb_batch ] [ -s ] [ -t ] [ -q ]
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[ -w start:stop ] [ -f output format ] [ -F format spec ]
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[ -d <binary> ]
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-i Input file containing trace data, or '-' for stdin.
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-D Directory to prepend to input file names.
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-o Output file. If not given, output is stdout.
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-b stdin read batching.
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-s Show per-program io statistics.
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-h Hash processes by name, not pid.
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-t Track individual ios. Will tell you the time a request took to
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get queued, to get dispatched, and to get completed.
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-q Quiet. Don't display any stats at the end of the trace.
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-w Only parse data between the given time interval in seconds. If
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'start' isn't given, blkparse defaults the start time to 0.
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-d Dump sorted data in binary format
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-f Output format. Customize the output format. The format field
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identifiers are:
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%a - Action
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%c - CPU ID
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%C - Task command (process) name
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%d - Direction (r/w)
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%D - Device number
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%e - Error number
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%M - Major
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%m - Minor
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%N - Number of bytes
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%n - Number of sectors
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%p - PID
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%P - PDU
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%s - Sequence number
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%S - Sector number
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%t - Time (wallclock - nanoseconds)
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%T - Time (wallclock - seconds)
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%u - Time (processing - microseconds)
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%U - Unplug depth
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-F Format specification. The individual specifiers are:
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A - Remap
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B - Bounce
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C - Complete
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D - Issue
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M - Back merge
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F - Front merge
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G - Get request
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I - Insert
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P - Plug
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Q - Queue
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R - Requeue
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S - Sleep requests
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T - Unplug timer
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U - Unplug IO
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W - Bounce
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X - Split
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-v More verbose for marginal errors.
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-V Print program version info.
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$ verify_blkparse filename
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Verifies an output file from blkparse. All it does is check if
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the events in the file are correctly time ordered. If an entry
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is found that isn't ordered, it's dumped to stdout.
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$ blkrawverify <dev> [<dev>...]
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The blkrawverify utility can be used to verify data retrieved
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via blktrace. It will check for valid event formats, forward
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progressing sequence numbers and time stamps, also does reasonable
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checks for other potential issues within invidividual events.
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Errors found will be tracked in <dev>.verify.out.
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If you want to do live tracing, you can pipe the data between blktrace
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and blkparse:
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% blktrace -d <device> -o - | blkparse -i -
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This has a small risk of displaying some traces a little out of sync, since
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it will do batch sorts of input events. Similarly, you can do traces over
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the network. The network 'server' must run:
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% blktrace -l
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to listen to incoming blktrace connections, while the client should use
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% blktrace -d /dev/sda -h <server hostname>
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to connect and transfer data over the network.
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Documentation
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-------------
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A users guide is distributed with the source. It is in latex, a
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'make docs' will build a PDF in doc/. You need tetex and latex installed
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to build the document.
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Resources
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---------
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vger hosts a mailing list dedicated to btrace discussion and development.
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The list is called linux-btrace@vger.kernel.org, subscribe by sending
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a mail to majordomo@vger.kernel.org with 'subscribe linux-btrace' in
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the mail body.
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2006-09-05, Jens Axboe <axboe@kernel.dk>
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