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    SubjectRe: Two fixes for 2.4.19-pre5-ac3
    On Sun, Apr 07, 2002 at 08:42:48PM +0100, Alan Cox wrote:

    > > I'll genuinely take on board advice on how I can profile all the system
    > > via x86 perf counters efficiently without having to patch the kernel.
    > > The old way just uses sys_call_table. So what do I do now ?
    >
    > The obvious thing is to represent it as a device. I'm not familiar enough
    > with the existing perfctr work to know how well that works out.

    The system call tracking is only used to associate a particular EIP with
    a particular offset in some binary image. There's no other efficient
    method to capture the mmap() calls for these images, for everything
    running. ptrace() is only really useful for a small number of processes,
    and is slow. Offline post-analysis isn't possible. There is no
    API for getting access to this information.

    Removing sys_call_table from exports won't have any positive effect.
    Using it has always been "well, you're on your own" - if there is a
    really good reason it needs to be changed, fine; but just changing it
    because it's not supposed to be used isn't a good enough reason when
    there is actually a couple of niche cases where it's the only option.

    imho,
    john

    --
    "I never understood what's so hard about picking a unique
    first and last name - and not going beyond the 6 character limit."
    - Toon Moene
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