542015 - Investigate the large startup performance difference between static and libxul static builds

Status: RESOLVED INCOMPLETE

(Firefox :: General, defect)

Description

[Joel Reymont (:joelr)]

I tried to narrow it via the build configuration but I think it goes deeper than that. Must be code that's compiled differently, depending on whether the LIBXUL build flag is on.

Comment 1

[Joel Reymont (:joelr)]

I think MOZ_ENABLE_LIBXUL is what makes the static libxul build faster. 

We do things differently in our build system and code, depending on whether libxul is enabled. MOZ_LIBXUL_ENABLED is used in about 50 files and some of them use different compile options (define flags, etc.) depending on whether MOZ_LIBXUL is enabled.

I don't think it's a productive use of our time to try to figure out what exactly makes a libxul build faster and we should just use it.

Comment 2

[Jeff Walden [:Waldo]]

...but it might make sense to do more of whatever it is that makes a libxul build faster, no?  And we can't know that without finding out what that is.

Comment 3

[Mark Banner (:standard8)]

I think we finished analysing performance of different loading styles ages ago. There doesn't seem to be much of use here.