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    SubjectRe: How how latent should non-preemptive scheduling be?
    Ingo Molnar wrote:
    > * Sitsofe Wheeler <sitsofe@yahoo.com> wrote:
    >
    >> Ingo Molnar wrote:
    >>> well, since they went away after you enabled CONFIG_PREEMPT=y, they are
    >>> definitely in-kernel latencies, not any external SMM latencies.
    >>>
    >>> I.e. they are inherently fixable. Could you enable:
    >>>
    >>> CONFIG_DYNAMIC_FTRACE=y
    >>> CONFIG_FTRACE_MCOUNT_RECORD=y
    >>>
    >>> that should make the traces a lot more verbose - every kernel function
    >>> executed in the latency path will be logged. That way we'll be able to
    >>> say which one takes that long.
    >> I do not appear to have the CONFIG_FTRACE_MCOUNT_RECORD option in
    >> 2.6.27rc7. Is it an option that is only in -tip ?
    >
    > yeah - it's a new ftrace feature queued up for v2.6.28.

    I've been struggling to boot -tip/master - currently it blows up just
    after printing SLUB information saying:

    BUG: unable to handle kernel NULL pointer dereference at 00000004
    IP: [<c0120078>] account_system_time+0x48/0x120
    *pde = 00000000
    Thread overran stack, or stack corrupted
    Oops: 0002 [#1] PREEMPT

    --
    Sitsofe | http://sucs.org/~sits/


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