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SubjectRe: tracepoint maintainance models

* Karim Yaghmour <karim@opersys.com> wrote:

> Theodore Tso wrote:
> > I *think* what Karim is trying to claim is that LTT also has some
> > dynamic capabilities, and isn't a pure static tracing system. But if
> > that's the case, I don't understand why LTT and SystemTap can't just
> > merge and play nice together....
>
> That's been the thrust of my intervention here. [...]

indeed, and i severely misunderstood your points in this regard. Now i
have re-read some of your earlier points, and in particular:

>> And finally, do realize that in 2000 I personally contacted the head
>> of the DProbes project IBM in order to foster common development,
>> following which ltt was effectively modified in order to allow
>> dynamic instrumentation of the kernel ...

and now i'm red faced - i was wrong about this fundamental aspect of
your position. Please accept my apologies!

so regarding the big picture we are largely on the same page in essence
i think - sub-issues non-withstanding :-) As long as LTT comes with a
facility that allows the painless moving of a static LTT markup to a
SystemTap script, that would come quite a bit closer to being acceptable
for upstream acceptance in my opinion.

The curious bit is: why doesnt LTT integrate SystemTap yet? Is it the
performance aspect? Some of the extensive hooking you do in LTT could be
aleviated to a great degree if you used dynamic probes. For example the
syscall entry hackery in LTT looks truly scary. I cannot understand that
someone who does tracing doesnt see the fundamental strength of
SystemTap - i think that in part must have lead to my mistake of
assuming that you opposed SystemTap.

Ingo
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