topic Number of physical CPUs in Operating System - Linux

Number of physical CPUs

Danesh Qureshi — Thu, 04 Oct 2007 09:01:23 GMT

I have a HP Proliant DL740 G1 server running
Red Hat Enterprise Linux AS release 3 (Taroon Update 4).

When I cat /proc/cpuinfo it displays 8 CPUs.

Does this mean this server has 8 phyical CPUs and if not how do I find out the number of physical CPUs in the server?

Re: Number of physical CPUs

Ivan Ferreira — Thu, 04 Oct 2007 09:14:34 GMT

Please see:

oss.intel.com/pdf/mclinux.pdf

Re: Number of physical CPUs

Heironimus — Thu, 04 Oct 2007 09:32:00 GMT

Each core of a multi-core processor will show up in cpuinfo, as will both halves of a hyperthreaded processor. If you want the number of physical chips you should look for the number of unique physical IDs listed in cpuinfo.

grep 'physical id' /proc/cpuinfo | sort -u

Re: Number of physical CPUs

Danesh Qureshi — Thu, 04 Oct 2007 10:18:37 GMT

# grep 'physical id' /proc/cpuinfo | sort -u
physical id : 0
physical id : 2
physical id : 4
physical id : 6

Please can you explain what the above output is telling me about the number of CPUs?

Re: Number of physical CPUs

David Claypool — Thu, 04 Oct 2007 10:40:14 GMT

The ProLiant DL740 was an 8 socket server and pre-dates the availability of multi-core processors. If cpuinfo is showing 8 CPUs and physical CPUs shows only 4, I would say that this indicates that you have 4 physical processors with HyperThreading enabled for a total of 8 logical processors.

If you have the 'hpasm' package loaded you can type:

hpasmcli "show server;show ht"

to get those details. The information also will show up when using the HP Systems Management Homepage or Insight Diagnostics.

Re: Number of physical CPUs

Ivan Ferreira — Thu, 04 Oct 2007 10:44:25 GMT

# grep 'physical id' /proc/cpuinfo | sort -u
physical id : 0
physical id : 2
physical id : 4
physical id : 6

This means that you have four physical processors, each one, with an ID. The values 0, 2, 4, 6 are the ID for each physical processor.