Posted Aug 7, 2007 22:34 UTC (Tue) by bcantrill
In reply to: static probes
Parent article: On DTrace envy
Frank, you write:
That's a pretty gutsy assertion
And a correct one, as we seem to be in vigorous agreement.
No, no we're not -- not at all. You wrote this:
...but almost all of the interesting
data that is gathered comes from providers other than fbt, and these
are implemented with static probes.
That is wrong
, and I am not in agreement with it whatsoever. It's wrong in two dimensions. The first being that "all...interesting data comes from providers other than fbt"; as I said (clearly, I thought) fbt
often are used as an investigation proceeds from the symptoms of a suboptimal system to the root-causes of that suboptimality in the implementation. So it's a gross mischaracterization to dismiss their role in DTrace. The second way in which your statement is incorrect is the implication that "providers other than fbt ... are implemented with static probes." This shows complete ignorance of the pid
provider, which can instrument any instruction in any running process, and is the workhorse of user-level instrumentation.
You also write:
from someone who, to the best of my knowledge, has never used DTrace.
The best of your knowledge needs to get better.
Fair enough; allow me to rephrase: "someone who, if they have used DTrace at all, appears to have learned nothing from the experience." Better?
to post comments)