Subject: Re: [patch 4/4] KVM-trace port to tracepoints
From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@qumranet.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       akpm@linux-foundation.org, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
       "Feng(Eric) Liu" <eric.e.liu@intel.com>
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Date: Wed, 23 Jul 2008 11:53:54 +0200
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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.

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