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    SubjectRe: kmemleak, cpu usage jump out of nowhere
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    On Thu, Jul 15, 2010 at 10:50 PM, Pekka Enberg <penberg@cs.helsinki.fi> wrote:
    > On Thu, Jul 15, 2010 at 11:38 PM, Zeno Davatz <zdavatz@gmail.com> wrote:
    >> Am 15.07.2010 um 22:00 schrieb Damien Wyart <damien.wyart@free.fr>:
    >>
    >>>>> For now, I can't reproduce the problem with CONFIG_NO_BOOTMEM disabled ;
    >>>>> with the option and rc5 the problem was happening quite quickly after
    >>>>> boot and normal use of the machine. So it seems I can confirme what Zeno
    >>>>> has seen and I hope this will give a hint to debug the problem. I guess
    >>>>> this has not been reported that much because many testers might not have
    >>>>> enabled CONFIG_NO_BOOTMEM... Maybe the scheduler folks could test their
    >>>>> benchmark with a kernel having this option enabled?
    >>>
    >>> * Pekka Enberg <penberg@cs.helsinki.fi> [2010-07-15 22:50]:
    >>>> To be honest, the bug is bit odd. It's related to boot-time memory
    >>>> allocator changes but yet it seems to manifest itself as a scheduling
    >>>> problem. So if you have some spare time and want to speed up the
    >>>> debugging process, please test v2.6.34 and v2.6.35-rc1 with
    >>>> CONFIG_NO_BOOTMEM and if former is good and latter is bad, try to see
    >>>> if you can identify the offending commit with "git bisect."
    >>>
    >>> Not sure I will have enough time in the coming days (doing that remotely
    >>> is fishy since ssh access is almost stuck when the problem occurs); if
    >>> Zeno can and would like to do it, maybe this could be done faster.
    >>>
    >>> As the scheduler is now very well instrumented (many debugging features
    >>> are available), reproducing the bug on a test platform (it happens quite
    >>> quickly for me) might also give some hints. So testers, if you have
    >>> time, please test 2.6.35-rc5 with CONFIG_NO_BOOTMEM on a Core i7 and see
    >>> if you can reproduce the problem!
    >>
    >> Will try to do so. Can you point me to the git bisect howto with the versions you want.
    >
    > Cool. So like I said, you first want to test 2.6.34 to find a known
    > good version. Please remember to make sure you have CONFIG_NO_BOOTMEM
    > enabled. You can also try to speed up the process by testing
    > 2.6.35-rc1 which is likely to include the offending commit. That's not
    > strictly necessary as long as you are sure that you have some
    > 2.6.35-rc kernel that's bad.
    >
    > After that, bisecting is as simple as:
    >
    >  git bisect start
    >  git bisect good v2.6.34
    >  git bisect bad v2.6.31-rc1 # or some other kernel you know to be bad
    >  <compile, boot, and try to trigger the problem>
    >
    > then
    >
    >  git bisect bad # if you were able to trigger the problem
    >
    > or
    >
    >  git bisect good # if the problem doesn't exist
    >
    > git will then find the next revision to test after which you do
    >
    >  <compile, boot, and try to trigger the problem>
    >
    > and repeat the "git bisect good/bad" step until git tells you it has
    > found the offending commit.
    >
    > There's more information on the git bisect man pages:
    >
    > http://www.kernel.org/pub/software/scm/git/docs/git-bisect.html
    >
    > Let me know if you need more help with this.

    The next RC again hangs on me:

    http://www.flickr.com/photos/zrr/4798744700/sizes/l/

    Gruss
    Zeno
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