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Beginner
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IPC sampling using PCM

Hi.

I want to get a lot of samples of IPC during the program execution. The program is sequential and lasts for a few seconds. The ideal is to collect samples every millisecond or every million retired instructions.

Command line, I do

./pcm.x 0.001 -csv=resul.txt "-- ./program"

but I don't know to finish sampling when program ends.

I think that it is better if the samples are taken into the program, but in this case I don't know to indicate the sampling period.

Thanks

JL

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Beginner
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J

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Employee
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you have to remove the "

./pcm.x 0.001 -csv=resul.txt -- ./program

the PCM overhead of collecting samples every ms may be too large. I would recommend to use >= 10 ms sampling period.

Thanks,

Roman

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Employee
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How about starting pcm in the background and then sending a signal (with "kill") to stop it?

Please note that you are truely pushing the limits with pcm measurements each millisecond. For larger systems, this is definitely too short.

 

Kind regards

Thomas

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Beginner
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Thanks,

I will adjust the period.

Next question: When using the option -csv, I obtain several IPC values (I   
suppose that they are associated to the different cores), even if I use
"taskset" for assigning the program to a given core.            

If I don't use the option -csv, the results offer something like this

 
Core (SKT) | EXEC | IPC  | FREQ  | AFREQ | L3MISS | L2MISS | L3HIT | L2HIT | L3MPI | L2MPI | TEMP
....               
.....

-------------------------------------------------------------------------------------------------              
SKT    0     0.08   1.32   0.06    0.96     197 K    572 K    0.66    0.34 0.00    0.00     50
SKT    1     0.00   0.31   0.00    0.47      20 K     36 K    0.45    0.10 0.01    0.02     58
-------------------------------------------------------------------------------------------------              
TOTAL  *     0.04   1.31   0.03    0.95     217 K    609 K    0.64    0.33 0.00    0.00     N/A


What value should I take?


I have also seen the options -nc and -ns of pcm.x command. Could I use to achieve my
goal?
               
Thanks

 

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Employee
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Hi Jose,

PCM collects statistics for all cores in the system. It does not restrict collection to the cores you have specified in the "taskset". PCM will display statistics (on the specified core) from your program and other programs that had been scheduled by the OS on this core. If you want statistics from your program only you need to use a different tool (Linux perf for example) that supports such functionality.

Best regards,

Roman

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Beginner
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Hi Roman,

I will try it with Linux perf.

Thanks again.

Best regards,

Jose L.

 

 

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