[webkit-dev] Growing tired of long build times? Check out this awesome new way to speed up your build... soon (HINT: It's not buying a new computer)

[Sam Weinig]

> On Aug 29, 2017, at 11:03 AM, Geoffrey Garen <ggaren at apple.com> wrote:
> 
>> I worry about adopting unity build because while it makes clean builds faster, it also slows down incremental builds. As a developer, I rarely do clean builds, I mostly do incremental builds so this would likely make my experience worse?
> 
> We have some preliminary data that says incremental builds will be OK, but not a full benchmark.
> 
> Here’s a full benchmark I propose to test incremental builds:
> 
> 	Start 7 days ago in SVN history. Do a clean build.
> 
> 	SVN update forward by 24 hours. Do an incremental build. Time this build.
> 
> 	Repeat 7 times. Average the results.
> 
> I think we should run this benchmark per project as we adopt unity builds, starting with WTF.
> 
> In the beginning, when we adopt unity builds for WTF and then JavaScriptCore, the benchmark can build just these projects and stop. Once we get to WebCore and WebKit, the benchmark will take longer. Oh well.
> 
> If we get the bundling right, this benchmark should show obvious speedups. If it shows no speedup or a slowdown, we’ve done something wrong and we need to reconsider.


This isn’t the scenario I find myself in most often.  A much more common scenario is working on a change; touch one or two files, and then compile and test/debug.  Rinse and repeat.

- Sam