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    SubjectRe: [PATCH] tracing: Cleanup the convoluted softirq tracepoints
    On Tue, Oct 19, 2010 at 07:05:15PM -0400, Steven Rostedt wrote:
    > On Tue, 2010-10-19 at 15:49 -0700, H. Peter Anvin wrote:
    > > On 10/19/2010 03:41 PM, Mathieu Desnoyers wrote:
    > > >>
    > > >> OK, first of all, there are some serious WTFs here:
    > > >>
    > > >> # define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
    > > >>
    > > >> A jump instruction is one of the worst possible NOPs. Why are we doing
    > > >> this?
    > > >
    > > > This code is dynamically patched at boot time (and module load time) with a
    > > > better nop, just like the function tracer does.
    > > >
    > >
    > > That's just ridiculous... start out with something sane and you at least
    > > have the chance of not having to patch it.
    >
    > Yep we can fix this. Jason?
    >

    sure. The idea of the 'jmp 0' was simply to be an lcd for x86, if
    there's a better lcd for x86, I'll update it. But note, that since the
    'jmp 0' is patched to a better nop at boot, we wouldn't see much gain.
    And in the boot path we are using 'text_poke_early()', so avoiding that
    isn't going to improve things much.

    I've got a few fixup patches in the queue that I'm going to post first,
    and then I'll take a look at this change.

    thanks,

    -Jason



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