通过单个进程计算 Total disk i/o

Question

I am looking for some tool that will dump total disk I/O by a single process after it ends. So far my finding is:-

• iotop = It shows i/o per process in real time but does not give total after process end.
• iostat = It shows real time I/O but does not tell process

For example , I have some process running in background with PID ####. I need the Total Bytes Written and Read by that process in total after the process ends.Can anybody tell how I can extract this information given a process PID.

Answer 1

Feel free to play with this scribble (myio.sh):

#!/bin/bash 

TEMPFILE=$(tempfile)    # create temp file for results

trap "rm $TEMPFILE; exit 1" SIGINT  # cleanup after Ctrl+C

SECONDS=0               # reset timer

$@ &                    # execute command in background

IO=/proc/$!/io          # io data of command
while [ -e $IO ]; do
    cat $IO > "$TEMPFILE"   # "copy" data
    sed 's/.*/& Bytes/' "$TEMPFILE" | column -t
    echo
    sleep 1
done

S=$SECONDS              # save timer

echo -e "\nPerformace after $S seconds:"
while IFS=" " read string value; do
    echo $string $(($value/1024/1024/$S)) MByte/s
done < "$TEMPFILE" | column -t

rm "$TEMPFILE"          # remove temp file

Syntax: ./myio.sh <your command>

Examples:

• ./myio.sh dd if=/dev/zero of=/dev/null bs=1G count=4096
• as root: ./myio.sh dd if=/dev/sda1 of=/dev/null bs=1M count=4096

Please change dd's of= in last example only if you know what you are doing.

---

With this simple script from me you can watch an already running process and its IO.

Syntax: pio.sh PID

#!/bin/bash

[ "$1" == "" ] && echo "Error: Missing PID" && exit 1
IO=/proc/$1/io          # io data of PID
[ ! -e "$IO" ] && echo "Error: PID does not exist" && exit 2
I=3                     # interval in seconds
SECONDS=0               # reset timer

echo "Watching command $(cat /proc/$1/comm) with PID $1"

IFS=" " read rchar wchar syscr syscw rbytes wbytes cwbytes < <(cut -d " " -f2 $IO | tr "\n" " ")

while [ -e $IO ]; do
    IFS=" " read rchart wchart syscrt syscwt rbytest wbytest cwbytest < <(cut -d " " -f2 $IO | tr "\n" " ")

    S=$SECONDS
    [ $S -eq 0 ] && continue

cat << EOF
rchar:                 $((($rchart-$rchar)/1024/1024/$S)) MByte/s
wchar:                 $((($wchart-$wchar)/1024/1024/$S)) MByte/s
syscr:                 $((($syscrt-$syscr)/1024/1024/$S)) MByte/s
syscw:                 $((($syscwt-$syscw)/1024/1024/$S)) MByte/s
read_bytes:            $((($rbytest-$rbytes)/1024/1024/$S)) MByte/s
write_bytes:           $((($wbytest-$wbytest)/1024/1024/$S)) MByte/s
cancelled_write_bytes: $((($cwbytest-$cwbytes)/1024/1024/$S)) MByte/s
EOF
    echo
    sleep $I
done

Answer 2

@Cyrus,

the unit for syscr and syswr is wrong, as it is not MByte/s but "operations/s"

rchar: number of bytes the process read, using any read-like system call (from files, pipes, tty...).
wchar: number of bytes the process wrote using any write-like system call.
syscr: number of read-like system call invocations that the process performed.
syscr: number of write-like system call invocations that the process performed.
read_bytes: number of bytes the process directly read from disk.
write_bytes: number of bytes the process originally dirtied in the page-cache (assuming they will go to disk later).
cancelled_write_bytes: number of bytes the process "un-dirtied" - e.g. using an "ftruncate" call that truncated pages from the page-cache.