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redhat - CPUs - show double what is installed

 
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Jeff Hoevenaar
Frequent Advisor

redhat - CPUs - show double what is installed

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?
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Steven E. Protter
Exalted Contributor
Solution

Re: redhat - CPUs - show double what is installed

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.

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Steven E Protter
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Ivan Ferreira
Honored Contributor

Re: redhat - CPUs - show double what is installed

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.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Vipulinux
Respected Contributor

Re: redhat - CPUs - show double what is installed

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
Jeff Hoevenaar
Frequent Advisor

Re: redhat - CPUs - show double what is installed

thanks for the info!