The state of DTrace

Hi guys,

Prompted by a recent thread I start to study dtrace, my first impression is : amazing tool !

I found some things perplexing though; I would like to know if any of you know something about it.

1] I don't find the pid provider. It should be there, at least according to this old page.
I use these commands to test
sudo dtrace -ln 'syscal*:::' | head
sudo dtrace -ln 'pi*:::' | head

2] I find the provider for ruby, cool to the n-th power, but i don't find the provider for sh, was it implemented ?
sudo dtrace -ln '*ruby*:::' | head
sudo dtrace -ln '*sh*:::' | head

3] The error below pops out quite frequently when I let D-scripts run for more than
a few seconds. It lastly appeared when i was watching the output of sudo dwatch -R execve

Assertion failed: (buf->dtbd_timestamp >= first_timestamp),
     file /usr/src/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c, line 3330.

I am running mostly FreeBSD-11.2, but I did a few test also on FreeBSD-12.0 (in BBB) and
it seems I get the same issues in both releases.