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I have a new four-blade Sandy bridge based platform running Debian "Wheezy" (7.1), but one of the blades is running consderably slower than the others (they're all configured identically). A ...
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  1. #1
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    Long processor hang times


    I have a new four-blade Sandy bridge based platform running Debian "Wheezy" (7.1), but one of the blades is running consderably slower than the others (they're all configured identically). A clue appears from dmesg, which has the line:

    hrtimer: interrupt took 921040 ns

    Indeed, looking at /proc/timer_list and grep-ing for "max_hang_time" shows:

    .max_hang_time : 522829 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 1767228 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 921040 nsecs
    .max_hang_time : 1003055 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 1244374 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs
    .max_hang_time : 0 nsecs

    By comparison, the the values on the other three blades are all 0 nsecs. I've set the CPU governor to "performance", and got it to ignore any BIOS setting. I've looked for any I/O related issues via iotop (there aren't any) and the node is using a fraction of its available memory (so no swapping involved). /var/log/mcelog is also empty, so no h/w errors are being reported there. So, what could be the possible reasons for these hang times?

    TIA

  2. #2
    Linux Guru Rubberman's Avatar
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    I can only conclude that the hardware is faulty - possibly a bad timer chip. Send it back for a replacement.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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