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What does it mean if Processor\Interrupts\Sec is high?

    Question

  • I have 2x Windows Server 2008 R2 on virtual machine environment. Virtualization is based on VMWare. I got hight values when I did performance testing with perfmon and SQL Profiler. What could be wrong?

    Server 1 results:
    Min value: 3265,00
    Max value: 4266,00
    Avg Value 3899,49

    Server 2 results:
    Min value: 3879,84
    Max value: 6414,43
    Avg Value: 4224,53

    I read following from Processor\Interrupts\Sec counter:
    Records the number of times processing is stopped to handle a hardware request for disk or memory I/O.
    Values higher than 1000 may indicate a hardware issue.


    Kenny_I
    Thursday, November 25, 2010 12:11 PM

All replies

  • Interrupts/sec is the average rate, in incidents per second, at which the processor received and serviced hardware interrupts. It does not include deferred procedure calls (DPCs), which are counted separately. This value is an indirect indicator of the activity of devices that generate interrupts, such as the system clock, the mouse, disk drivers, data communication lines, network interface cards, and other peripheral devices. These devices normally interrupt the processor when they have completed a task or require attention. Normal thread execution is suspended. The system clock typically interrupts the processor every 10 milliseconds, creating a background of interrupt activity. This counter displays the difference between the values observed in the last two samples, divided by the duration of the sample interval

    Start digging around for what could be causing the interrupts.  I would look at your disk subsystem first.

     

    Bruce


    Bruce Adamczak
    • Marked as answer by Kenny_I Wednesday, December 01, 2010 10:27 AM
    • Unmarked as answer by Kenny_I Wednesday, December 01, 2010 10:28 AM
    Tuesday, November 30, 2010 10:08 PM
    Moderator
  • Thanks.

    Does it mean that if we are able tune the server and get Interrupt/sec value down under 1000, the server performance would increase? Is it possible that in some case high Interrupt/sec values does not actually affect performance?


    Kenny_I
    Wednesday, December 01, 2010 10:31 AM
  • I'm not sure where the threshold of 1000 came from.  As processors get faster then we can handle more interrups/sec.  

    So depending when this tool / white paper was written it might be correct for what was current hardware at that time.

    You also need to be looking at this over time.  A single high spike could mean nothing.  A substain high value could indicate hardware issue.

    It best to keep your drivers upto date. 

    Here is a good link to start with to understand how to look for server bottle necks.

    http://technet.microsoft.com/en-us/magazine/2008.08.pulse.aspx?pr=blog

    Bruce

     

     

     


    Bruce Adamczak
    Wednesday, December 01, 2010 10:00 PM
    Moderator