decoding of multi-byte nops in dtrace

Ryan Stone rysto32 at gmail.com
Sun Jun 10 20:40:54 UTC 2012


On Sun, Jun 10, 2012 at 12:38 PM, Andriy Gapon <avg at freebsd.org> wrote:
> Interesting observations, thank you.
> Do you use -O2 or higher optimization for kernel/modules build?
> I use only -O1.
>
> Here are some stats from my system:
> $ dtrace -ln fbt::: | fgrep -c entry
> 16876
> $ dtrace -ln fbt::: | fgrep -c return
> 16729
>
> So, 147 functions without return probe.

Try re-compiling with -foptimize-sibling-calls.  That enables the tail
call optimization in gcc, and therefore you get many functions with no
ret instruction (and thus no return probe in DTrace)


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