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    SubjectRe: [ANNOUNCE] New utility: 'trace'
    On Wed, Nov 17, 2010 at 01:13:40PM -0500, Ted Ts'o wrote:
    > On Wed, Nov 17, 2010 at 03:10:33PM +0100, Frederic Weisbecker wrote:
    > > Yeah I have a strange workflow. I'm working on that CPU isolation thing
    > > and I have dozens of trace_printk all over the place for tons of
    > > things. And everytime I remove one to unwind some output or to focus
    > > on another one, I often have to restore it later because I need it
    > > again. Usually I even just comment it out instead of removing it.
    >
    > What I do for my file system development work is to drop in
    > trace_printk's everywhere, since they are lightweight and don't slow
    > down the system much. Then when the system wedges, I use sysrq-z to
    > get a "flight data recorder" printout of what happened up til the
    > system hung.
    >
    > I love the fact that the ring buffer is in "overwrite" mode (aka
    > flight data recorder mode), and hope this doesn't go away.
    >
    > Per line filtering is also great, but very often when I'm interacting
    > with the block I/O layer, if something screws up, what happens is "and
    > then whole machine locks up", and sysrq-z is literally all I have.

    Yeah all agreed.

    Steve proposed to keep the current trace_printk() implementation that relies
    on ftrace but rename in into ftrace_printk(). So that we can develop a new
    trace_printk() based on trace_event interface and in the meantime keep the
    old version in case something messes up with the new thing.



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