Here is another example from gstat:
CPUs (Procs/Total) [ 1, 5, 15min] [ User, Nice, System, Idle,
Wio]
8 ( 8/ 122) [ 4.59, 2.04, 1.35] [ 99.8, 0.0,
0.2,-67062349824.0,-67062349824.0] OFF
Looking at the source code for AIX metrics
(https://github.com/ganglia/monitor-core/blob/master/libmetrics/aix/metrics.
c), it appears that negative values should be converted to 0. This is
either not happening or the metrics are somehow being modified after the
fact.
g_val_t
cpu_wio_func ( void )
{
g_val_t val;
get_cpuinfo();
val.f = CALC_CPUINFO(wait);
if(val.f < 0) val.f = 0.0;
return val;
}
g_val_t
cpu_idle_func ( void )
{
g_val_t val;
get_cpuinfo();
val.f = CALC_CPUINFO(idle);
if(val.f < 0) val.f = 0.0;
return val;
}
From: K. Hansen
Sent: Wednesday, October 02, 2013 4:50 PM
To: ganglia-general@lists.sourceforge.net
Subject: Insane negative values for cpu_idle and cpu_wio when node is CPU
bound
Environment:
AIX 6.1 TL7 SP7
gmond 3.6.0 (from http://www.perzl.org/ganglia/)
I noticed that a particular node would send insanely high negative values
for cpu_idle and cpu_wait metrics when cpu_user + cpu_system were near 100%,
i.e. the node is completely CPU bound. The result is major skewing of the
node's cpu_idle and cpu_wio graphs so that no true positive values are
visible, and the cpu_report graph for the node, cluster, and grid become
corrupted.
Here is an example of what I am talking about: http://imgur.com/a/aIzyU
I am able to replicate this behavior on any AIX node by running the
following command to generate CPU load:
perl -e 'while (--$ARGV[0] and fork) {}; while () {}' 8
Where the last digit is the number of threads available to the server. For
example, if a server has 2 POWER7 vCPU, then it has 8 threads (logical CPU)
due to 4-way simultaneous multithreading (SMT).
Has anyone else experienced this on AIX or Linux?
Thanks!
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