WAS 5.1 and multicore server... Only using one core??? - Websphere

This is a discussion on WAS 5.1 and multicore server... Only using one core??? - Websphere ; We have a 4-way Windows 2003 server but never see the underlying java.exe process (WAS) using more than 25% of the total processing power. Processor affinity (through the task manager) is set to allow it to run on all four ...

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Thread: WAS 5.1 and multicore server... Only using one core???

  1. WAS 5.1 and multicore server... Only using one core???

    We have a 4-way Windows 2003 server but never see the underlying java.exe process (WAS) using more than 25% of the total processing power. Processor affinity (through the task manager) is set to allow it to run on all four cores. How is it possible to make WAS 5.1.1.16 use more than one core on this server so we don't have it sitting idle 75% of the time?

    Thanks!
    Andy

  2. Re: WAS 5.1 and multicore server... Only using one core???

    > We have a 4-way Windows 2003 server but never see the underlying java.exe
    > process (WAS) using more than 25% of the total processing power.
    > Processor affinity (through the task manager) is set to allow it to run on
    > all four cores. How is it possible to make WAS 5.1.1.16 use more than one
    > core on this server so we don't have it sitting idle 75% of the time?


    WebSphere is fully capable of using all cores you throw at it.

    To verify this, code a JSP which does a busy loop for a few seconds:
    ---- busy.jsp ----
    Begin.
    <%
    out.flush();
    long before = System.currentTimeMillis();
    while (System.currentTimeMillis() < (before + 20 * 1000)) {
    // busy loop for a number of seconds
    }
    %>
    Finished.
    -------

    Then point your browser at the page and look at the CPU usage, you're now
    consuming 25%.

    Hit the refresh button (before the 20 seconds ellapse), and you're now
    consuming 50%. Hit again to consume 75% and again to go to 100%.

    Wait a few seconds, and you'll see usage nicely decrease from 100% to 75%,
    50%, 25% and idle.

    So, if you're consuming "only" 25% CPU, the problem is not WebSphere, but
    the application.

    Probably, there are synchronized constructs in the application (or the
    libraries it uses) which prevent execution in parralel and thereby prevent
    WebSphere from using the four cores.

    Or you're not putting enough load at it. Or it's waiting on I/O (network,
    disk, etc). Or ...

    Welcome to the wonderful world of performance troubleshooting. :-)


  3. Re: WAS 5.1 and multicore server... Only using one core???

    I suggest using Ben's example to test your load-balancing.
    If you still see it never going above 25%, perhaps there is some
    property in WAS that is not set correctly to use multiple cores.
    The O/S (Windows Server 2003, in this case) should handle the
    load-balancing among the cores; being transparent to the processes that
    are running.

    I would think that an application server as heavy-weight as WAS should
    handle multiple cores "out of the box."

    If Ben's example does indeed show up to 100% usage, then be happy that
    your current load on your Application Server is only consuming 25% of
    your processing power and remember you have plenty of room to grow.
    :-)

    --Jason

    ajmiller@mandtbank.com wrote:
    > We have a 4-way Windows 2003 server but never see the underlying java.exe process (WAS) using more than 25% of the total processing power. Processor affinity (through the task manager) is set to allow it to run on all four cores. How is it possible to make WAS 5.1.1.16 use more than one core on this server so we don't have it sitting idle 75% of the time?
    >
    > Thanks!
    > Andy


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