[Libreoffice] gnumake / dependencies 20%+ speedup ...

[Michael Meeks]

Hi there,

On Mon, 2011-09-05 at 11:36 +0100, Caolán McNamara wrote:
> On Fri, 2011-09-02 at 21:22 +0100, Michael Meeks wrote:
> > 	Or are they there in fact there for some good purpose that I just
> > failed to spot ? :-)
> 
> Yes, I added all these deliberately. See
> http://www.makelinux.net/make3/make3-CHP-8-SECT-3 for the rationale.

	Ah indeed :-)

> The outcome is that on incremental builds when someone removes a header
> and nothing includes it anymore, the build doesn't break with some
> bizarro error but "does the right thing". For me the build-time
> difference is negligible but I guess its significant for others.

	So that is great. Of course the build-time difference is indeed
negligable, but the incremental build time impact is quite real.

	So - we need these rules in place; with a small tweak to my script to
print the dummy rules we'd be throwing away, I notice that we have (eg.)

    483 /data/opt/libreoffice/core/sc/inc/rangelst.hxx:
    634 /data/opt/libreoffice/core/sc/inc/address.hxx:
    719 /data/opt/libreoffice/core/sc/inc/global.hxx:
    797 /data/opt/libreoffice/core/sc/inc/scdllapi.h:

	several hundred duplicate dummy rules for many headers - still
consuming big chunks of the aggregated library dependency files. That
yields 441k redundant lines instead of 445k - but I think that's most of
the win ;-)

	I attach an updated cleanup.pl - that leaves the dummy rules, but
removes duplicates in them; it takes a second or two to run itself ;-)
[ we could write it in C no doubt to accelerate it if that is an issue
]. Which gmake rule builds the aggregated library dependency file that
could have this wedged into it ?

	Thoughts ?

	ATB,

		Michael.

-- 
 michael.meeks at novell.com  <><, Pseudo Engineer, itinerant idiot

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