How to find the process that is doing io on Linux


If  you need to find out which process is doing io on your Linux server maybe these steps help to find the process.

  • First  Save  this  Script as  "iodump"

#!/usr/bin/env perl

=pod

=head1 NAME

iodump - Compute per-PID I/O stats for Linux when iotop/pidstat/iopp are not available.

=head1 SYNOPSIS

Prepare the system:

dmesg -c
/etc/init.d/klogd stop
echo 1 > /proc/sys/vm/block_dump

Start the reporting:

while true; do sleep 1; dmesg -c; done | perl iodump
CTRL-C

Stop the system from dumping these messages:

echo 0 > /proc/sys/vm/block_dump
/etc/init.d/klogd start

=head1 LICENSE

This software is released to the public domain, with no guarantees whatsoever.

=cut

use strict;
use warnings FATAL => 'all';
use English qw(-no_match_vars);
use sigtrap qw(handler finish untrapped normal-signals);

my %tasks;

my $oktorun = 1;
my $line;
while ( $oktorun && (defined ($line = <>)) ) {
my ( $task, $pid, $activity, $where, $device );
( $task, $pid, $activity, $where, $device )
= $line =~ m/(\S+)\((\d+)\): (READ|WRITE) block (\d+) on (\S+)/;
if ( !$task ) {
( $task, $pid, $activity, $where, $device )
= $line =~ m/(\S+)\((\d+)\): (dirtied) inode \(.*?\) (\d+) on (\S+)/;
}
if ( $task ) {
my $s = $tasks{$pid} ||= { pid => $pid, task => $task };
++$s->{lc $activity};
++$s->{activity};
++$s->{devices}->{$device};
}
}

printf("%-15s %10s %10s %10s %10s %10s %s\n",
qw(TASK PID TOTAL READ WRITE DIRTY DEVICES));
foreach my $task (
reverse sort { $a->{activity} <=> $b->{activity} } values %tasks
) {
printf("%-15s %10d %10d %10d %10d %10d %s\n",
$task->{task}, $task->{pid},
($task->{'activity'}  || 0),
($task->{'read'}      || 0),
($task->{'write'}     || 0),
($task->{'dirty'}     || 0),
join(', ', keys %{$task->{devices}}));
}

sub finish {
my ( $signal ) = @_;
if ( $oktorun ) {
print STDERR "# Caught SIG$signal.\n";
$oktorun = 0;
}
else {
print STDERR "# Exiting on SIG$signal.\n";
exit(1);
}
}
  • Then turn on kernel messages  about I/O:

#echo 1 > /proc/sys/vm/block_dump
  • This makes the kernel start writing messages about every I/O operation that takes place. Now all you have to do is get those messages and feed them into the iodump script:

# while true; do sleep 1; dmesg -c; done | perl iodump
^C# Caught SIGINT.
TASK                   PID      TOTAL       READ      WRITE      DIRTY DEVICES
firefox               4450       4538        251       4287          0 sda4, sda3
kjournald             2100        551          0        551          0 sda4
firefox              28452        185        185          0          0 sda4
kjournald              782         59          0         59          0 sda3
pdflush                 31         30          0         30          0 sda4, sda3
syslogd               2485          2          0          2          0 sda3
firefox              28414          2          2          0          0 sda4, sda3
  • When finished, turn off kernel messages about I/O:

#echo 0 > /proc/sys/vm/block_dump

 

I'm a IT Infrastructure and Operations Architect with extensive experience and administration skills and works for Turk Telekom. I provide hardware and software support for the IT Infrastructure and Operations tasks.

205 Total Posts
Follow Me

0 Comments

Leave a Reply