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

From: Martin Bligh
Date: Thu Sep 14 2006 - 16:26:20 EST


if there are lots of tracepoints (and the union of _all_ useful tracepoints that i ever encountered in my life goes into the thousands) then the overhead is not zero at all.

also, the other disadvantages i listed very much count too. Static tracepoints are fundamentally limited because:

- they can only be added at the source code level

- modifying them requires a reboot which is not practical in a
production environment

- there can only be a limited set of them, while many problems need
finegrained tracepoints tailored to the problem at hand

- conditional tracepoints are typically either nonexistent or very
limited.

for me these are all _independent_ grounds for rejection, as a generic kernel infrastructure.

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.

M.
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