Include gc samples in raw output about stackprof HOT 3 CLOSED

Ooh, this is very cool!

A fake stack frame for GC is a good idea. Please do submit a PR.

from stackprof.

Great! I'll look into it.

From a quick skim of the source, it's not clear to me why rb_postponed_job_register_one is used rather than just invoking stackprof_job_handler directly from stackprof_signal_handler.

From reading https://balazs.kutilovi.cz/post/ruby-tracing-part-two-rbtrace/, it sounds like postponed jobs are run when the process receives a signal, but isn't stackprof_signal_handler already only called due to a signal being received?

Is it necessary because otherwise the stack will include only the stackprof_signal_handler itself?

The only reason I ask is because I'm unsure whether I'd need to use rb_postponed_job_register_one to add the sample for the fake GC frame, or if I can do that synchronously within a function call from stackprof_job_handler.

from stackprof.

The issue that a signal can come in at any time, including for example when the Ruby VM is setting up a method call. It is not safe to get a ruby stack trace while the ruby stack itself is being manipulated and may be inconsistent. Doing so would quickly segfault the process.

Thus we use the postponed_job api to grab a stack trace as soon as the VM is consistent enough to do so.

For the GC case, I think you can just add the frame directly since you're only touching stackprof state and not doing anything with the VM.

from stackprof.