Re: [patch 4/4] KVM-trace port to tracepoints

Peter Zijlstra
2008-07-23T09:54:43Z

On Wed, 2008-07-23 at 12:32 +0300, Avi Kivity wrote:
> Peter Zijlstra wrote:
> > There are currently no trace_mark() sites in the kernel that I'm aware
> > of (except for the scheduler :-/, and those should be converted to
> > tracepoints ASAP).
> >
> > Andrew raised the whole point about trace_mark() generating an
> > user-visible interface and thus it should be stable, and I agree with
> > that.
> >
> > What that means is that trace_mark() can only be used for really stable
> > points.
> >
> > This in turn means we might as well use trace points.
> >
> > Which allows for the conclusion that trace_mark() is not needed and
> > could be removed from the kernel.
> >
> > However - it might be handy for ad-hoc debugging purposes that never see
> > the light of day (linus' git tree in this case). So on those grounds one
> > could argue against removing trace_mark
>
> But trace_mark() is so wonderful.

I guess tastes differ...

> Can't we just declare the tracemarks
> as a non-stable interface?
>
> Perhaps add an unstable_trace_mark() to make it clear.

At the very least it would need its own output channel. But I'm afraid
this will be KS material.