Re: [ltt-dev] Linux Trace terminology - feedback requested

[Michel Dagenais <michel.dagenais@polymtl.ca>]

> Have you heard of any system that does that effectively?  In systemtap
> we've found that it is not unusual for the kernel compiler to mangle
> code and data flows so much that there is little hope for an
> arbitrarily placed *comment* ("compiled out") to be preserved in a
> sensible way.

This is unfortunately very true. Perhaps you can leave a label or a
special directive that effectively reserves that location in the code
and somewhat limits what the optimizer will do there.

> This distinction seems to offer little value.  A really compiled-out
> static probe is just as useful as a dynamic-probe script that is not
> running.
...
> If, on the other hand, "compiled-out" means something milder, like
> leaving a number of NOPs in the object code, then we should consider a
> different term, since even NOPs don't come free.

Then indeed we may need a name for these things; do we have something in
the source code, is there something in the binary (NOPS place holder,
conditional instruction...).