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static probes

static probes

Posted Aug 8, 2007 8:06 UTC (Wed) by njs (guest, #40338)
In reply to: static probes by bcantrill
Parent article: On DTrace envy

Not the interrupt the Flame-War of the Titans, but...

When Frank sez "almost all of the interesting data that is gathered comes from providers other than fbt", I don't think he's saying "no-one ever uses fbt". (Nor is he trying to estimate total number of in-production probe hits on different providers or anything like that.) He's replying to a claim that static probes are irrelevant, or uninteresting, or at least not as important as the original article claimed. Maybe cajal didn't mean his comment that way, but it certainly can be read that way.

Based on that, to me it basically sounds like Frank is saying "static providers are critical to dtrace's usability in practice", and you're saying "no, no, static providers are only critical to do initial investigation of problems so you can figure out how to deploy the other parts of dtrace". These are not exactly contradictory statements. I can't imagine trying to do anything with dtrace without relying on proc, sched, io, even if I used fbt and pid too.

So cajal's comment does seem a bit misleading, and it seems fair to correct that part of it.

(FTR, I haven't used dtrace either, just envied it intensely.)

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static probes

Posted Aug 8, 2007 13:22 UTC (Wed) by cajal (subscriber, #4167) [Link]

I was responding to the original article's claim that "SystemTap, instead, does not depend on static probe points within the kernel". That claim implies that DTrace depends on static probe points in the kernel. I was only trying to point out that DTrace provides both dynamic and static trace points (since, as Bryan points out, both are needed).

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