02February2017 [FreeBSD WIKI]

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====== DTrace Hangout Notes 02 Feb 2017 ======

  * gnn@ to create a mailing list associated with %%OpenDTrace%%

  * gnn@ has finished 

  * markj@ has put a change to USDT relocations ([[https://reviews.freebsd.org/D9374]]) that addresses the use of undefined behavior in the linker.  rwatson@ points out that there are several folks on the project with linker experience at the moment.

  * domagoj@ has looked into how to better integrate his virtual machine RFD with the work being done by Graeme on CADETS.  domagoj@ would like to eliminate the need for zookeeper to identify the nodes.  rwatson@ says that we are more interested in getting the distributed DTrace thing correct.  For the purposes of hypervisors rwatson@ does not think we should not converge these two things but take advantage of the fact that hypervisors do not have the communication issues that networked systems do.

  * There remains the question of where to keep the probe list, in the kernel or in user space.  Domagoj suggests that it can remain in the kernel in a matrix.  rwatson@ suggests that we experiment with the simplest possible system and that points us back towards the kernel.

  * James asks about updating scripts on the fly.  rwatson@ says that this is done in the DDTrace system by updating the DIF on the fly.  The question is bast asked of Graeme.

  * gnn@ says he'll be submitting RFDs for if() and do/while().

  * gnn@ has imported the lastest xnu and macos-dtrace tarballs into the opendtrace repos

  * shrikanth@ wants to talk about CTF sections becoming huge when dealing with more embedded systems.  shrikanth@ and the Juniper folks are looking at being able to load the CTF sections on demand.  markj@ says that this should be doable with libproc but that this has not yet been MFC'd to STABLE/11.  James says that they'd like to move to DWARF since all their other tools are DWARF but that has only been a prototype.  There is a CTF compressed flag but no one knows is the sections are actually compressed or not.

  * rwatson@ mentions that emaste@ is working on libelf like things and gnn@ will talk to him about CTF features in that arena

  * Domgaoj asks about having anonymous tracing switch to using a file once we've gone multi-user.  markj@ thinks we'll need a filesystem to make this all work so there is a question of where to switch over.

  * We'd like to bring over the stack tracing for Python.  Isilon does have patches for this, but they're invasive.  

  * gnn@ will ask Graeme about the patches to libdtrace that might still be outstanding.

  * Damogoj is looking at instance local variables.

  * Those with access to Phabricator should join the DTrace group therein