lkml.org 
[lkml]   [2007]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Subjecttime accounting problem (powerpc only?)
    From
    Date
    Hi,

    On my powerbook, with NO_HZ and HIGH_RES_TIMERS, I observed recently
    that powernowd would not ever switch between CPU speeds.

    Doing some scripting to read /proc/stat every half second and print the
    differences, I get output like this on a mostly idle system:

    # for reference:
    # [user, nice, system, idle, iowait, irq, softirq, steal, guest]

    [4, 0, 3, 46, 0, 264, 0, 0, 0]
    [5, 0, 4, 41, 0, 266, 0, 0, 0]
    [4, 0, 7, 37, 0, 299, 0, 0, 0]

    Now starting an empty while (1) loop, I see:

    [53, 0, 1, 0, 0, 243, 0, 0, 0]
    [53, 0, 2, 0, 0, 224, 0, 0, 0]
    [45, 0, 7, 0, 0, 249, 0, 0, 0]

    As you can see, the "irq" time is very high so that "user" (mostly my
    CPU burning program) only accounts for maybe 15%. This leads to
    powernowd thinking that all is fine and no switching is required. Also,
    the whole stuff leads to top(1) displaying about 80-90% "hi" (hard irq?
    calculated as irq - softirq?) time.

    Does anybody have an idea why the irq time is so high? And no, I don't
    think it can actually be true, I'm seeing maybe 500 interrupts/second
    (most due to USB).

    johannes

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-11-23 13:19    [W:0.043 / U:1.004 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site