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    SubjectRe: [GIT PULL] x86/cpu changes for v2.6.34


    On Mon, 1 Mar 2010, Frederic Weisbecker wrote:

    > On Mon, Mar 01, 2010 at 09:00:58AM +0100, Ingo Molnar wrote:
    > >
    > > if (smp_processor_id() == 7)
    > > ftrace_enabled = 1;
    > >
    > > ... bootup sequence ...
    > >
    > > if (smp_processor_id() == 7)
    > > ftrace_enabled = 0;

    > So, after the boot you can look at /debug/tracing/per_cpu/cpu7/trace
    > and the end of the trace should contain what you want.

    Both of you seemed to miss the fact that it's not cpu7 that is
    particularly slow. See the original email from me in this thread: the jump
    was at some random point:

    [ 0.245179] CPU 1 MCA banks CMCI:2 CMCI:3 CMCI:5 SHD:6 SHD:8
    [ 0.265332] #2
    [ 0.353185] CPU 2 MCA banks CMCI:2 CMCI:3 CMCI:5 SHD:6 SHD:8
    [ 0.373328] #3
    [ 2.193277] CPU 3 MCA banks CMCI:2 CMCI:3 CMCI:5 SHD:6 SHD:8
    [ 2.213379] #4

    and the reason I grepped for "CPU 7" was that it's the _last_ CPU on this
    machine, so what I was grepping for was basically "how long did it take to
    bring up all CPU's".

    So that particular really bad case apparently happened for CPU#3, but the
    two other slow cases happened for CPU#4.

    Also, it seems to happen only about every fifth boot or so. Suggestions
    for something simple that can trace things like that?

    Linus


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