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

Avi Kivity
2008-07-23T08:08:31Z

Peter Zijlstra wrote:
> On Tue, 2008-07-22 at 21:46 +0300, Avi Kivity wrote:
>
>> Jan Kiszka wrote:
>>
>>> That's true - as long as you don't have to add/remove/modify
>>> tracepoints. I had to do this job in the past (not for KVM). Having 1
>>> spot in 1 file (based on generic probes) would be handier in that case
>>> than 5 spots in 3 files. But if the KVM tracepoints are considered
>>> stable in their number and structure, that shouldn't be an issue here.
>>>
>>>
>>>
>> Tracepoints aren't stable; they are artefacts of the implementation.
>>
>
> Which IMHO makes it unsuitable for trace_mark() as that will be exported
> to user-space, and every time you change your tracepoints you'll change
> user visible things - not nice.
>

They are used for debugging (mostly performance related), so changes are
expected.

What uses of trace_mark() depend on a stable interface? blktrace?

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