1318002 - Split perfherder build_metrics by clobber vs. dep build

Status: RESOLVED INCOMPLETE

(Firefox Build System :: General, defect)

Description

[(not currently active) Ted Mielczarek]

Dep build times are always going to be variable by nature--they're building on top of an already-built objdir, so they have a variable amount of work to do depending on the changes from the previous revision to the current revision. Clobber builds should be more consistent.

It would be good if we could indicate which type of build we did in the perfherder build metrics so we could get a reasonably consistent graph for clobber build times, and then whatever noisy mess we get for dep builds.

I don't know how easy this is to define right now--AIUI there are two ways to clobber a build (the in-tree CLOBBER file, and a per-build-type clobber mechanism), there's also the case of "we just didn't have an existing objdir handy" that causes us to do a full build, and then I don't actually know what nightly and try builds do, but they always do a full clobber build.

Comment 1

[Gregory Szorc [:gps]]

Yeah, detecting a clobber build here is definitely the hard part. My initial instinct is building the detection into `mach build` feels like the best place, as it knows about CLOBBER and path to the objdir. It would also be useful to record "is clobber" in the JSON resource usage file so when that file is uploaded we can bucket accordingly.

Comment 2

[(not currently active) Ted Mielczarek]

I guess there are really only two cases here we'd need to handle if we do this in the build system:
1) The objdir does not exist, so we're doing a clobber build.
2) The objdir does exist but CLOBBER was touched and we have `AUTOCLOBBER=1` set, so we're forcing a clobber from within the build system.

Those should be straightforward to detect from within the build system, I believe. The try/nightly/clobbered from mozharness cases should all fall into bucket 1, since the objdir won't exist by the time `mach build` is invoked.

Comment 3

[(not currently active) Ted Mielczarek]

In light of bug 1456969 this isn't particularly important right now.