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    SubjectRe: [RFC PATCH 1/2] Marker probes in futex.c
    On Thu, 2008-04-17 at 18:02 -0400, Frank Ch. Eigler wrote:
    > Peter Zijlstra <> writes:
    > > [...]
    > >> If we were to log just the futex_ops, just as you had suggested,
    > >> "Just log:
    > >>
    > >> futex: <uaddr> wait
    > >> futex: <uaddr> wakeup"
    > >> [...]
    > >> If you can specifically point me to information you think would be
    > >> absolutely unnecessary, I can get them out of the trace_mark().
    > >
    > > I'm thinking everything is superflous; you're basically logging what
    > > strace already gives you
    > But we don't want to run strace just for this stuff. As you probably
    > know, strace involves invasive user-space context-switching between
    > the target and the tracer.
    > > except worse by encoding local variable names and exposing kernel
    > > pointers.
    > The pointers are probably excessive, the and the names don't really
    > matter.

    Then what do we do when someone comes along and changes one of those
    names; do we go around changing the markers and then requiring all tools
    to change as well?

    (And no this isn't far fetched; I'm thinking of changing fshared in the
    near future).

    Sounds like people will complain and generate back pressure against such
    changes - something we should avoid. As soon as these markers place a
    significant burden on code maintenance I'm against it.

    > What does matter is providing enough information for a
    > problem diagnosis tool & person to reconstruct what the kernel must
    > have been thinking when it did something noteworthy.

    Sure, but then just make a strace like tracer and be done with it - no
    need to pollute the futex code with that.

     \ /
      Last update: 2008-04-18 08:49    [W:0.020 / U:18.472 seconds]
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