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navyant
Beginner
94 Views

Very low IPC with VTune and others...

Hello,
I've tested vtune with a couple of spec2000 (with reference input) under Redhat 7.3 Linux using a Pentium 4 machine and got follow very low IPC which seems unreasonable. This is the command I put into

vtl activity -duration 300 -c sampling -o "-ec en='Instructions Retired' en='Clockticks':sa=200000 " -app mcf_base.x86_linux,"inp.in" run

Instructions Retired
17400 = Samples collected due to this event
2000000 = Sample after value used during collection
34800000000 = Total events (samples*SAV)
Clockticks
704881 = Samples collected due to this event
200000 = Sample after value used during collection
140976200000 = Total events (samples*SAV)

So IPC is about 1/4.5 (348/1409)

With bzip, I got a IPC of 1/2. Other benchmarks show a constant less than 1 of IPCs.

Another strange thing is whenever I changed duration, the instructions retired gives different results. I am surely I have run the whole program from the beginning to the end.

Anything wrong with my usage. Thanks!
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1 Reply
David_A_Intel1
Employee
94 Views

Recommendations:

1. don't set a duration: VTune will sample until the app exits.
2. don't set a sample after value for Clockticks, the default should be used.

Regards,
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