topic Re: redhat - CPUs - show double what is installed in Operating System - Linux

redhat - CPUs - show double what is installed

Jeff Hoevenaar — Mon, 16 Jan 2006 10:09:50 GMT

I have a ProLiant DL580 G3 with 4 CPUs installed. But when I look at the /proc/cpuinfo it shows 8 CPUs installed. Also, when I run the "top" command it shows 8 CPUs.

Why is that?

Re: redhat - CPUs - show double what is installed

Steven E. Protter — Mon, 16 Jan 2006 10:14:05 GMT

Shalom Jeff,

Your CPU's have hyperthreading enabled. That is a virtual, software CPU, built into the hardware CPU. By default, it is enabled in the BIOS.

The OS see's the number of CPU's based on the virtual count.

4 hardware cpu's equal 8 top cpu's in this scenario.

Gets you 60% performance bump over older cpu's.

SEP

Re: redhat - CPUs - show double what is installed

Ivan Ferreira — Mon, 16 Jan 2006 10:26:19 GMT

You have hyperthreading enabled, and you can see the real number of cpu by their physical ID. You will have two processors with the same physical ID.

Re: redhat - CPUs - show double what is installed

Vipulinux — Mon, 16 Jan 2006 12:29:04 GMT

Hi

If the system has hyperthreading than it will show 1 CPU as 2
eg if ur system has 2 cpu it will show as 4.

In order to have alook at the real no. of CPU's do
cat /proc/cpuinfo

Cheers

Re: redhat - CPUs - show double what is installed

Jeff Hoevenaar — Mon, 16 Jan 2006 12:34:08 GMT

thanks for the info!