Re: plockstat

On Mon, May 09, 2016 at 11:11:33AM +0100, Doug Rabson wrote:
> Is plockstat supposed to work on FreeBSD? I'm running FreeBSD-current and
> when I try it, I get:
> 
> plockstat: failed to compile program: probe description
> plockstat65047:::rw-block does not match any probes
> 
> Any ideas what to try next?

Unfortunately, the plockstat probes have not been implemented in libthr,
so there's nothing for plockstat(1) to use. I think it should probably
be disconnected from the build until that's addressed.

One of my colleagues at Isilon has done a proof-of-concept
implementation of plockstat-like probes. It uses the support in share/mk
for adding USDT probes, so the integration is pretty simple: one just
adds the .d script containing provider definitions to SRCS.

The patch is here:
https://people.freebsd.org/~markj/patches/isi_plockstat.diff

I just extracted it from an internal repo; some work may be needed for
it to apply to head/.

There's a bit more work needed to integrate USDT probes into the source
tree. dtrace -G has problems with incremental rebuilds that would need
to be fixed first. However, it works fine otherwise - the DTrace test
suite build creates a number of programs containing USDT probes.

-Mark