Re: [PATCH v2 1/5] Documentation/Makefile: conditionally include doc.dep

[Felipe Contreras <felipe.contreras@gmail.com>]

On Sun, Dec 6, 2020 at 6:35 PM Ramsay Jones <ramsay@ramsayjones.plus.com> wrote:
>
>
> The 'clean' target is noticeably slow on cygwin, even for a 'do-nothing'
> invocation of 'make clean'. For example, the second 'make clean' below:
>
>   $ make clean >/dev/null 2>&1
>   $ make clean
>   GIT_VERSION = 2.29.0
>   ...
>   make[1]: Entering directory '/home/ramsay/git/Documentation'
>       GEN mergetools-list.made
>       GEN cmd-list.made
>       GEN doc.dep
>   ...
>   $
>
> has been timed at 23.339s, using git v2.29.0, on my laptop (on old core
> i5-4200M @ 2.50GHz, 8GB RAM, 1TB HDD).
>
> Notice that, since the 'doc.dep' file does not exist, make takes the
> time (about 8s) to generate several files in order to create the doc.dep
> include file. (If an 'include' file is missing, but a target for the
> said file is present in the Makefile, make will execute that target
> and, if that file now exists, throw away all its internal data and
> re-read and re-parse the Makefile). Having spent the time to include
> the 'doc.dep' file, the 'clean' target immediately deletes those files.
>
> In order to eliminate such wasted effort, use the value of the internal
> $(MAKECMDGOALS) variable to only '-include doc.dep' when the target is
> not 'clean'. (This drops the time down to 12.364s, on my laptop, giving
> an improvement of 47.02%).

All this makes sense, but I had to do "make doc.dep" and take a look
at that file to understand why:

doc.dep contains make rules with targets and dependencies that will
not be used in "make clean".

This is in my opinion the important information. Maybe mention
something like that in the commit message?

Cheers.

-- 
Felipe Contreras