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  • Latest Post - ‏2010-05-12T14:10:41Z by SystemAdmin
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Pinned topic Controlling SMT on boot on POWER7

‏2010-05-05T21:20:52Z |
On SLES 11 running on POWER7,
I will prefer to start with no SMT, how do you control this ?
I saw that the command "ppc64_cpu --smt... " can set the SMT mode "off, 2 or 4" ..
I guess this is "root/superuser's privledge command?
Updated on 2010-05-12T14:10:41Z at 2010-05-12T14:10:41Z by SystemAdmin
  • SystemAdmin
    SystemAdmin
    706 Posts

    Re: Controlling SMT on boot on POWER7

    ‏2010-05-05T22:18:21Z  
    You can boot the system directly into SMT=off mode by adding an smt-enabled=off string to the append directive in the /etc/lilo.conf file on SLES 11.

    For what it's worth, the ppc64_cpu command that shipped with SLES 11 last year is a little out of date, and cannot correctly set the SMT modes on POWER7.

    If you see this, you have the out-of-date version.
    
    # ppc64_cpu Usage: ppc64_cpu --smt             # Get current SMT state ppc64_cpu --smt=
    {on|off
    }    # Set SMT state   ppc64_cpu --dscr            # Get current DSCR setting ppc64_cpu --dscr=<val>      # Change DSCR setting   ppc64_cpu --smt-snooze-delay # Get currentsmt-snooze-delay setting ppc64_cpu --smt-snooze-delay=<val> # Change smt-snooze-delay setting
    


    Check out: http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils

    Yes, ppc64_cpu is a root access command.

    There are ways to setup HPC environments which will allow jobs to set the right SMT level for each job. This would only be useful when jobs are assigned the whole compute node.
  • SystemAdmin
    SystemAdmin
    706 Posts

    Re: Controlling SMT on boot on POWER7

    ‏2010-05-12T14:10:41Z  
    You can boot the system directly into SMT=off mode by adding an smt-enabled=off string to the append directive in the /etc/lilo.conf file on SLES 11.

    For what it's worth, the ppc64_cpu command that shipped with SLES 11 last year is a little out of date, and cannot correctly set the SMT modes on POWER7.

    If you see this, you have the out-of-date version.
    <pre class="jive-pre"> # ppc64_cpu Usage: ppc64_cpu --smt # Get current SMT state ppc64_cpu --smt= {on|off } # Set SMT state ppc64_cpu --dscr # Get current DSCR setting ppc64_cpu --dscr=<val> # Change DSCR setting ppc64_cpu --smt-snooze-delay # Get currentsmt-snooze-delay setting ppc64_cpu --smt-snooze-delay=<val> # Change smt-snooze-delay setting </pre>

    Check out: http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils

    Yes, ppc64_cpu is a root access command.

    There are ways to setup HPC environments which will allow jobs to set the right SMT level for each job. This would only be useful when jobs are assigned the whole compute node.
    By the way, there are several other FAQs on controlling and understanding SMT behavior on the Performance FAQs page.

    Check out: http://www.ibm.com/developerworks/wikis/display/LinuxP/Performance+FAQs