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    SubjectRe: [PATCH 0/3] ftrace: overrun accounting and trace_pipe headers

    On Tue, 22 Apr 2008, Pekka Paalanen wrote:

    > Excellent!

    Thanks ;-)

    > On Mon, 21 Apr 2008 17:09:35 -0400
    > Steven Rostedt <> wrote:
    > > The first patch in this series adds accounting to record overruns. That is
    > > where the writing catches up to the reading of the buffer. This really
    > > only matters for trace_pipe since that's a consumer / producer output file.
    > This takes me some thinking how to make the best of it, but looks like it
    > allows me to relay the overrun events into the trace log. Very good.
    > > The next patch adds new methods for the plugins to hook into the
    > > open_pipe and open_read, to let a plugin produce a header.
    > > The open_read method can also be used to do something when overruns
    > > are detected.
    > You mean pipe_open() and read()? :-)
    > And read() is pipe specific?

    Yeah the read API is pipe specific (for now). I'll have to think about
    whether or not we should have a generic "read" and a "pipe_read"

    > Ah, now I see what you mean by read() can be used to notice overruns:
    > it is called for every read syscall, not just in the beginning.


    > > The last patch is a test patch AND SHOULD NOT BE APPLIED. It is just an
    > > example in how to use the new methods to produce a header. It simply
    > > makes the ftrace tracer produce a simple "Test header" before any
    > > output.
    > In function_read(), shouldn't I be doing something with filp and/or ppos?

    Probably, that's why I said not to apply it ;-)


    -- Steve

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