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OpenMP and CPU usage

Hi

I was using a program in C on my personnal computer which used parallelization with OpenMP. It worked fine until i tried to use it on an Openstack instance.

Here's what i get when i use top command on my personnal computer when using the program (12 cores Intel(R) Xeon(R) CPU X5650 @ 2.67GHz). This is the expected behaviour

Normal behaviour

Here's what i get when i use top command on the openstack machine when using the program (8 cores Intel Xeon E312xx (Sandy Bridge) @ 2599.998 Mhz)

Unexpected behaviour

Multiple questions here:

  1. When i do a cat /proc/cpuinfo on the openstack machine, it tells me that the proc is a Xeon E312xx. Isn't it a cpu family? because that's what i get when i look it up on google. How can i know the exact model?

  2. We can see that threads are not using full CPU usage and are sometimes put to sleep, which never happened on my computer (always have 99.9~% on each threads). How come they are put to sleep. It's not due to memory usage or swaping since i'm barely using them.

Sorry, my knowledge is really low on UNIX systems and even lower on openstack.

Thanks by advance

Best regards

OpenMP and CPU usage

Hi

I was using a program in C on my personnal computer which used parallelization with OpenMP. It worked fine until i tried to use it on an Openstack instance.

Here's what i get when i use top command on my personnal computer when using the program (12 cores Intel(R) Xeon(R) CPU X5650 @ 2.67GHz). This is the expected behaviour

Normal behaviour

Here's what i get when i use top command on the openstack machine when using the program (8 cores Intel Xeon E312xx (Sandy Bridge) @ 2599.998 Mhz)

Unexpected behaviour

Multiple questions here:

  1. When i do a cat /proc/cpuinfo on the openstack machine, it tells me that the proc is a Xeon E312xx. Isn't it a cpu family? because that's what i get when i look it up on google. How can i know the exact model?

  2. We can see that threads are not using full CPU usage and are sometimes put to sleep, which never happened on my computer (always have 99.9~% on each threads). How come they are put to sleep. It's not due to memory usage or swaping since i'm barely using them.

Sorry, my knowledge is really low on UNIX systems and even lower on openstack.

Thanks by advance

Best regards