1.6Gb of workdir/.../Dep - thoughts ...

[Bjoern Michaelsen]

On Mon, Jun 04, 2012 at 06:38:46PM +0200, Michael Stahl wrote:
> who cares how big the files are (disk is cheap), the relevant metric is:
> how many seconds does make need to parse them?
> ...
> yes, but keep in mind that variables in the dep files will need to be
> expanded by make, which will likely result in memory allocations, so
> it's an open question whether that will actually improve performance or
> slow it down.

IIRC I made some measurements back then. Though not very scientific, they
suggested it makes no difference at all.

> >> - a significant part of .d content is the depend-on-nothing deps created 
> >> by -MP , if those would be merged into one dedicated .d file that'd save a 
> >> lot of space as well; not sure if this is easily doable though
> > 
> > Arent we doing that already when merging the .d files for one library?
> 
> to some extent yes, but of course the same headers are included in many
> libraries, so there is still some amount of duplication there; however i
> don't know to improve this without breaking separate building of
> modules, which requires the LinkTarget .d files to be self-contained.
> 
> > So right now, I consider the topic premature optimization until proven otherwise.
> 
> > (*) which you wont unless you gzip them (which is doable and shouldnt have too
> > big of an performance impact)
> 
> sadly AFAIK make cannot include compressed files...

We never include the dep-files of the objects ( $(WORKDIR)/Dep/CxxObject ),
only the concated per-library output ( $(WORKDIR)/Dep/LinkTarget ), right?

Best,

Bjoern