Sampling interval

[joehoyle]

Taken from phacility#80, same patch but refreshed. Needs accreditation.

[Slach]

Failed to build with php7 sampling-interval branch with following errors

/opt/xhprof/extension/xhprof.c:2025:19: error: 'zval' has no member named 'type'
   } else if(values->type == IS_STRING) {
                   ^
Makefile:193: recipe for target 'xhprof.lo' failed
make: *** [xhprof.lo] Error 1

full log here
https://pastebin.com/mheCFree
;(

[nathanielks]

I'm curious why the tests were removed?

[nathanielks]

Excuse me, it was just one test file! Nevermind!

[joehoyle]

@nathanielks this PR had the wrong base, I've updated that now, but it wasn't intended to be merged anyway.

[nathanielks]

I'll leave it be 😄

[rmccue]

@joehoyle I feel like we should just merge this and start maintaining it as a full repo, given we're running in production.

[rmccue]

And by "merge this" I mean, merge sampling-interval into experimental, and merge experimental into master. I'd say we should probably also rip out the non-extension directories.

I can get in touch with Phacility again if we want?

[joehoyle]

@rmccue yeah I think that's a good idea. No idea what Phacility are doing!

Also, MediaWiki it looks like chose not to go this route as they were seeing large overheads, which I have not been able to replicate (see https://phabricator.wikimedia.org/T176916). They are exploring other ways to instrument function enter / exits. It's worth us continuing to monitor what solution they come up with as we are essentially wanting to do the same thing (low-overhead flame graphs)