Mailing List Archive

On Wed, 8 Jun 2005, Andy Smith wrote:

> Using 2.0-testing, what methods are people using to monitor
> individual domU CPU usage?
>
> Obviously I can run an snmpd in each domU and see how busy the CPU
> is, but that could be tampered with from inside the domU, and as the
> domU doesn't know it doesn't have the whole cpu needs some
> interpretation.
>
> I can see CPU time used in "xm list" but that looks like rather a
> blunt tool - would I have to do something like this for example:

AFAIK, from what you describe you don't have much choice, you are going to
have to watch from _both_ the inside and the outside. I guess you might be
able to guess which domU is requesting CPU if the total CPU on the box
goes to 100%.

I have a script that polls xm list ever 60 seconds and logs the results.
From this I can get a feeling for what % of the CPU is being consumed and
which dom is using it...

e.g.

[root@xen1 ~]# more ~tbrown/uptime.log.xen
Wed Jun 8 00:00:01 PDT 2005
Domain-0 2.48% cpu usage 102461.38 sec over 47.91 days
domain-dns 16.91% cpu usage 501043.99 sec over 34.30 days
mailman 0.70% cpu usage 6938.28 sec over 11.53 days
mx 27.56% cpu usage 605861.02 sec over 25.44 days

1 7 1 20 68
1 11 2 27 55
3 96 0 35 -36
2 48 0 26 21
1 8 0 32 56
1 5 0 31 60
2 6 0 38 51
1 12 0 21 64
2 13 0 34 49
2 21 0 36 37
1 8 0 31 57
2 14 0 34 48


Where the columns are the doms in the order described in the header... and
the last column being idle time.

hhmm, the script is only 67 lines... I will include it...
The polling frequency and number of samples to take are
commandline parameters, I run it hourly as "script 60 59" in my
crontab.

here goes:

#!/usr/bin/perl
#
# script to dump CPU stats for VMs
#
# vim:ai

use strict;

my $interval = shift || 5;
my $num_samples = shift || 0;

my $uptime = `cat /proc/uptime`;
$uptime =~ s/ .*$//g; # trim from first space, should leave us uptime in
secs

my $XM="/usr/sbin/xm";


my $loop = 0;
my $lasttimestamp = 0;
my %lastcpu = ();
while ( ++$loop ) { # loop forever
my $buf = '';
my $count = 0;
my $dat = `$XM list -l`
or die "no output from $XM list ?? maybe it isn't in your path?";
my $datatimestamp = time();
$dat =~ tr/\(\)/{}/; # for readability of regex below.
my $totcpu = 0;

while ( my($dom,$rest) = ($dat =~ m/^(.*?\n})(.*)$/gs ) ) {
my ($domcpu) = ($dom =~ m/{cpu_time\s([\d\.]+)}/)
or die "couldn't extract cpu_time from $dom on dom $count\n";
my ($domup) = $uptime;
if ($count > 0 ) {
($domup) = ($dom =~ m/{up_time\s([\d\.]+)}/)
or die "couldn't extract up_time from $dom on dom $count\n";
}
my $domname = "dom-$count";
{
my ($tmp) = ($dom =~ m/{name\s(.+)}/);
$domname = $tmp if ($tmp);
}

if ($loop <= 1) {
$buf .= sprintf "%10s %5.2f%% cpu usage %.2f sec over %.2f days\n",
$domname, 100 * $domcpu/$domup, $domcpu, $domup/24/3600;
} else {
my $cpu = $domcpu-$lastcpu{$count};
$totcpu += $cpu;
$buf .= sprintf "%3d ",
100 * $cpu/$interval;
}
$lastcpu{$count} = $domcpu;
$dat = $rest;
$count++;
die "count exceeded" if ($count > 100);
}
my $period = ($datatimestamp - $lasttimestamp);
if ($loop > 1) { # add on idle cpu
$buf .= sprintf "%3d", 100 * ($interval - $totcpu)/$period;
}
$lasttimestamp = $datatimestamp;
print "$buf\n";
exit if ($num_samples && $loop > $num_samples);
sleep $interval;
}


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