[Beowulf] How to debug slow compute node?

Faraz Hussain info at feacluster.com
Thu Aug 10 07:39:07 PDT 2017

One of our compute nodes runs ~30% slower than others. It has the  
exact same image so I am baffled why it is running slow . I have  
tested OMP and MPI benchmarks. Everything runs slower. The cpu usage  
goes to 2000%, so all looks normal there.

I thought it may have to do with cpu scaling, i.e when the kernel  
changes the cpu speed depending on the workload. But we do not have  
that enabled on these machines.

Here is a snippet from "cat /proc/cpuinfo". Everything is identical to  
our other nodes. Any suggestions on what else to check? I have tried  
rebooting it.

processor       : 19
vendor_id       : GenuineIntel
cpu family      : 6
model           : 62
model name      : Intel(R) Xeon(R) CPU E5-2670 v2 @ 2.50GHz
stepping        : 4
cpu MHz         : 2500.098
cache size      : 25600 KB
physical id     : 1
siblings        : 10
core id         : 12
cpu cores       : 10
apicid          : 56
initial apicid  : 56
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge  
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe  
syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts  
rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor  
ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2  
x2apic popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm ida  
arat xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid  
fsgsbase smep erms
bogomips        : 5004.97
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

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