Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108

[Jes Sorensen]

>>>>> "Ingo" == Ingo Molnar <mingo@xxxxxxx> writes:

Ingo> * Martin Bligh <mbligh@xxxxxxxxxx> wrote:

>> I don't think anyone is saying that static tracepoints do not have
>> their limitations, or that dynamic tracepointing is useless. But
>> that's not the point ... why can't we have one infrastructure that
>> supports both? Preferably in a fairly simple, consistent way.

Ingo> primarily because i fail to see any property of static tracers
Ingo> that are not met by dynamic tracers. So to me dynamic tracers
Ingo> like SystemTap are a superset of static tracers.

Ingo> So my position is that what we should concentrate on is to make
Ingo> the life of dynamic tracers easier (be that a handful of
Ingo> generic, parametric hooks that gather debuginfo information and
Ingo> add NOPs for easy patching), while realizing that static tracers
Ingo> have no advantage over dynamic tracers.

The parallel that springs to mind here is C++ kernel components 'I
promise to only use the good parts', then next week someone else adds
another pile in a worse place. Once the points are in we will never
get rid of them, look at how long it took to get rid of devfs :( In
addition it is guaranteed that people will not be able to agree on
which points to put where, despite the claim that there will be only
30 points - sorry, I am not buying that, we have plenty of evidence to
show the opposite.

I looked at the old LTT code a while ago and it was pretty appalling,
maybe LTTng is better, but I can't say the old code gave me a warm
fuzzy feeling.

Jes
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