Hi Khrist:
I'm not sure if he is working off our main GitHub repo but if he is, you
might want to patch it and submit a pull request.
Thanks for your support!
Cheers,
Bernard
On Thursday, 3 October 2013, Khrist Hansen wrote:
> This appears to be an issue with Mr. Perzl's updated libperfstat code
> borrowed from IBM's perfstat_cpu_total example.
>
> ftp://www.oss4aix.org/ganglia/RPMs-3.3.7/src/ganglia-3.3.7-aix.patch
>
>
> http://publib.boulder.ibm.com/infocenter/aix/v6r1/topic/com.ibm.aix.prftools
> /doc/prftools/idprftools_perfstat_glob_cpu.htm
>
> When calculating wio and idle, the code performs a divide operation with
> (dlt_lcpu_wait + dlt_lcpu_idle) as the divisor. If the server is CPU
> bound,
> i.e. usr+sys=100%, then both dlt_lcpu_wait and dlt_lcpu_idle will be zero,
> and the division will occur with zero as the divisor.
>
> This should be a fairly simple fix, and I am attempting to contact Mr.
> Perzl
> to that effect.
>
>
> -----Original Message-----
> From: Khrist Hansen [mailto:[email protected] <javascript:;>]
> Sent: Wednesday, October 02, 2013 6:18 PM
> To: [email protected] <javascript:;>
> Subject: RE: Insane negative values for cpu_idle and cpu_wio when node is
> CPU bound
>
> 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: [email protected] <javascript:;>
> 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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