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232 lines
7.2 KiB
Bash
Executable File
232 lines
7.2 KiB
Bash
Executable File
#!/bin/bash
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#
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# iosnoop - trace block device I/O.
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# Written using Linux ftrace.
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#
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# This traces disk I/O at the block device interface, using the block:
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# tracepoints. This can help characterize the I/O requested for the storage
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# devices and their resulting performance. I/O completions can also be studied
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# event-by-event for debugging disk and controller I/O scheduling issues.
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#
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# USAGE: ./iosnoop [-hst] [-d secs] [-p pid] [-n name]
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#
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# REQUIREMENTS: FTRACE CONFIG, block:block_rq_* tracepoints (you may
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# already have these on recent kernels).
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#
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# OVERHEAD: By default, iosnoop works without buffering, printing I/O events
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# as they happen (uses trace_pipe), context switching and consuming CPU to do
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# so. This has a limit of about 10,000 IOPS (depending on your platform), at
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# which point iosnoop will be consuming 1 CPU. The "-d secs" mode uses buffering,
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# and can handle much higher IOPS rates, however, the buffer has a limit of
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# about 50,000 I/O, after which events will be dropped. You can tune this with
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# bufsize_kb, which is per-CPU. Also note that the "-n" option is currently
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# post-filtered, so all events are traced.
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#
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# This was written as a proof of concept for ftrace. It would be better written
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# using perf_events (after some capabilities are added), which has a better
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# buffering policy, or a tracer such as SystemTap or ktap.
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#
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# From perf-tools: https://github.com/brendangregg/perf-tools
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#
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# See the iosnoop(8) man page (in perf-tools) for more info.
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#
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# COPYRIGHT: Copyright (c) 2014 Brendan Gregg.
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public License
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# as published by the Free Software Foundation; either version 2
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# of the License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software Foundation,
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# Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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#
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# (http://www.gnu.org/copyleft/gpl.html)
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#
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# 12-Jul-2014 Brendan Gregg Created this.
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### default variables
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tracing=/sys/kernel/debug/tracing
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flock=/var/tmp/.ftrace-lock
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bufsize_kb=4096
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opt_duration=0; duration=; opt_name=0; name=; opt_pid=0; pid=; ftext=
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opt_start=0; opt_end=0
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trap ':' INT QUIT TERM PIPE # sends execution to end tracing section
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function usage {
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cat <<-END >&2
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USAGE: iosnoop [-hst] [-d secs] [-p PID] [-n name]
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-d seconds # trace duration, and use buffers
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-n name # process name to match on I/O issue
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-p PID # PID to match on I/O issue
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-s # include start time of I/O (s)
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-t # include completion time of I/O (s)
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-h # this usage message
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eg,
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iosnoop # watch block I/O live (unbuffered)
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iosnoop -d 1 # trace 1 sec (buffered)
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iosnoop -p 181 # trace I/O issued by PID 181 only
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END
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exit
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}
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function warn {
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if ! eval "$@"; then
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echo >&2 "WARNING: command failed \"$@\""
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fi
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}
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function die {
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echo >&2 "$@"
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exit 1
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}
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### process options
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while getopts d:hn:p:st opt
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do
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case $opt in
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d) opt_duration=1; duration=$OPTARG ;;
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n) opt_name=1; name=$OPTARG ;;
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p) opt_pid=1; pid=$OPTARG ;;
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s) opt_start=1 ;;
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t) opt_end=1 ;;
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h|?) usage ;;
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esac
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done
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shift $(( $OPTIND - 1 ))
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### option logic
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(( opt_pid && opt_name )) && die "ERROR: use either -p or -n."
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(( opt_pid )) && ftext=" issued by PID $pid"
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(( opt_name )) && ftext=" issued by process name \"$name\""
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if (( opt_duration )); then
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echo "Tracing block I/O$ftext for $duration seconds (buffered)..."
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else
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echo "Tracing block I/O$ftext. Ctrl-C to end."
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fi
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### ftrace lock
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[[ -e $flock ]] && die "ERROR: ftrace may be in use by PID $(cat $flock) $flock"
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echo $$ > $flock || die "ERROR: unable to write $flock."
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### select awk
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(( opt_duration )) && use=mawk || use=gawk # workaround for mawk fflush()
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[[ -x /usr/bin/$use ]] && awk=$use || awk=awk
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### setup and begin tracing
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cd $tracing || die "ERROR: accessing tracing. Root user? Kernel has FTRACE?"
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echo nop > current_tracer
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warn "echo $bufsize_kb > buffer_size_kb"
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if (( opt_pid )); then
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if ! echo "common_pid==$pid" > events/block/block_rq_issue/filter; then
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die "ERROR: setting -p $pid. Continuing..."
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fi
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fi
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if ! echo 1 > events/block/block_rq_issue/enable || \
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! echo 1 > events/block/block_rq_complete/enable; then
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die "ERROR: enabling block I/O tracepoints. Exiting."
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fi
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(( opt_start )) && printf "%-14s " "STARTs"
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(( opt_end )) && printf "%-14s " "ENDs"
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printf "%-16.16s %-6s %-4s %-8s %-12s %-6s %8s\n" \
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"COMM" "PID" "TYPE" "DEV" "BLOCK" "BYTES" "LATms"
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#
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# Determine output format. It may be one of the following (newest first):
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# TASK-PID CPU# |||| TIMESTAMP FUNCTION
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# TASK-PID CPU# TIMESTAMP FUNCTION
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# To differentiate between them, the number of header fields is counted,
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# and an offset set, to skip the extra column when needed.
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#
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offset=$($awk 'BEGIN { o = 0; }
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$1 == "#" && $2 ~ /TASK/ && NF == 6 { o = 1; }
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$2 ~ /TASK/ { print o; exit }' trace)
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### print trace buffer
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warn "echo > trace"
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( if (( opt_duration )); then
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# wait then dump buffer
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sleep $duration
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cat trace
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else
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# print buffer live
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cat trace_pipe
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fi ) | $awk -v o=$offset -v opt_name=$opt_name -v name=$name \
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-v opt_duration=$opt_duration -v opt_start=$opt_start -v opt_end=$opt_end '
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# common fields
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$1 != "#" {
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# task name can contain dashes
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comm = pid = $1
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sub(/-[0-9][0-9]*/, "", comm)
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sub(/.*-/, "", pid)
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time = $(3+o); sub(":", "", time)
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dev = $(5+o)
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}
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# block I/O request
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$1 != "#" && $0 ~ /rq_issue/ {
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if (opt_name && match(comm, name) == 0)
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next
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#
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# example: (fields1..4+o) 202,1 W 0 () 12862264 + 8 [tar]
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# The cmd field "()" might contain multiple words (hex),
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# hence stepping from the right (NF-3).
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#
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loc = $(NF-3)
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starts[dev, loc] = time
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comms[dev, loc] = comm
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pids[dev, loc] = pid
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next
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}
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# block I/O completion
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$1 != "#" && $0 ~ /rq_complete/ {
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#
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# example: (fields1..4+o) 202,1 W () 12862256 + 8 [0]
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#
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dir = $(6+o)
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loc = $(NF-3)
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nsec = $(NF-1)
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if (starts[dev, loc] > 0) {
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latency = sprintf("%.2f",
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1000 * (time - starts[dev, loc]))
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comm = comms[dev, loc]
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pid = pids[dev, loc]
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if (opt_start)
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printf "%-14s ", starts[dev, loc]
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if (opt_end)
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printf "%-14s ", time
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printf "%-16.16s %-6s %-4s %-8s %-12s %-6s %8s\n",
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comm, pid, dir, dev, loc, nsec * 512, latency
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if (!opt_duration)
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fflush()
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delete starts[dev, loc]
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delete comms[dev, loc]
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delete pids[dev, loc]
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}
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next
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}
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$0 ~ /LOST.*EVENTS/ { print "WARNING: " $0 > "/dev/stderr" }
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'
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### end tracing
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echo 2>/dev/null
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echo "Ending tracing..." 2>/dev/null
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if ! echo 0 > events/block/block_rq_issue/enable || \
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! echo 0 > events/block/block_rq_complete/enable; then
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echo >&2 "ERROR: disabling block I/O tracepoints."
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exit 1
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fi
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(( opt_pid )) && warn "echo 0 > events/block/block_rq_issue/filter"
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warn "echo > trace"
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warn "rm $flock"
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