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  • Latest Post - ‏2009-08-10T12:56:07Z by SystemAdmin
SystemAdmin
SystemAdmin
706 Posts

Pinned topic Hyperthreading enabled or disabled?

‏2009-08-10T09:52:03Z |
Hi All,

How can I know whether a machine (RHEL 5.3 on ppc64 processor) is hyper-threading enabled/disabled? I know it is enabled in BIOS, but how can I check it through commands and disable it?

The below gives information regrading HT on linux but does not give any info on disabling it in BIOS -
http://dag.wieers.com/blog/is-hyper-threading-enabled-on-a-linux-system

Please give some inputs on HT on power machines.
thanks,
Sanjay
Updated on 2009-08-10T12:56:07Z at 2009-08-10T12:56:07Z by SystemAdmin
  • SystemAdmin
    SystemAdmin
    706 Posts

    Re: Hyperthreading enabled or disabled?

    ‏2009-08-10T12:18:11Z  
    On Power, it's called SMT.

    Use the command ppc64_cpu --smt to see/control it. You'll need root access.

    Linux sees each core as two logical CPUs ie: cpu0 and cpu1 would be one core.
    If you disable (turn off) SMT, the "odd numbered CPUs" are turned off.

    For a before example, with SMT=on, we look at top (after the "1" key has been pressed)

    This is from an 8-core p6 system.

    
    top - 08:11:37 up 19:50,  1 user,  load average: 0.05, 0.01, 0.00 Tasks: 238 total,   1 running, 237 sleeping,   0 stopped,   0 zombie Cpu0  :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.5%hi,  0.0%si,  0.0%st Cpu1  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu2  :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.5%hi,  0.0%si,  0.0%st Cpu3  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu4  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu5  :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.5%hi,  0.0%si,  0.0%st Cpu6  :  0.0%us,  0.5%sy,  0.0%ni, 99.1%id,  0.0%wa,  0.5%hi,  0.0%si,  0.0%st Cpu7  :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.0%hi,  0.5%si,  0.0%st Cpu8  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu9  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu10 :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.5%hi,  0.0%si,  0.0%st Cpu11 :  0.0%us,  0.0%sy,  0.0%ni, 99.1%id,  0.0%wa,  0.5%hi,  0.5%si,  0.0%st Cpu12 :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu13 :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu14 :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.5%hi,  0.0%si,  0.0%st Cpu15 :  0.0%us,  0.5%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Mem:  130742336k total,  4413568k used, 126328768k free,   788800k buffers
    


    Then to view, turn off, and then confirm that SMT is off:

    
    # ppc64_cpu --smt smt is on # ppc64_cpu --smt=off # ppc64_cpu --smt smt is off
    

    Now, top (after "1" key pressed)

    
    top - 08:13:36 up 19:52,  1 user,  load average: 0.00, 0.00, 0.00 Tasks: 158 total,   1 running, 157 sleeping,   0 stopped,   0 zombie Cpu0  :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.2%wa,  0.2%hi,  0.0%si,  0.0%st Cpu2  :  0.0%us,  0.0%sy,  0.0%ni, 99.8%id,  0.0%wa,  0.2%hi,  0.0%si,  0.0%st Cpu4  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu6  :  0.0%us,  0.0%sy,  0.0%ni, 99.3%id,  0.2%wa,  0.2%hi,  0.2%si,  0.0%st Cpu8  :  0.0%us,  0.0%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.2%hi,  0.2%si,  0.0%st Cpu10 :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st Cpu12 :  0.0%us,  0.0%sy,  0.0%ni, 99.8%id,  0.0%wa,  0.2%hi,  0.0%si,  0.0%st Cpu14 :  0.0%us,  0.0%sy,  0.0%ni, 99.8%id,  0.0%wa,  0.0%hi,  0.2%si,  0.0%st Mem:  130742336k total,  4409984k used, 126332352k free,   788992k buffers
    
  • SystemAdmin
    SystemAdmin
    706 Posts

    Re: Hyperthreading enabled or disabled?

    ‏2009-08-10T12:56:07Z  
    Hi,
    If I need to check the same SMT status on x86_64 linux machine, what could be the command to enable and disable?

    Thanks,