Re: which build is the fastest?
Bruno Haible <[email protected]> Tue, 23 Jan 2018 20:02:45 +0100
| Newsgroups | gmane.lisp.clisp.devel |
|---|---|
| Message-ID | <3563587.lnKge5obtf@omega> |
Hi Sam,
> > If you give a man a toy, he will play with it.
> > Now that we have all those multibuild targets in Makefile.devel, we can
> > find out which build is the fastest (e.g., if I make small
> > architecture-agnostic change, which build do I test it in?)
This is something you can easily find out, by putting a 'time' command
in Makefile.devel and then running a 'multibuild-<platform>' target with '-k'.
In my experience, the following factors are important (in decreasing order
of importance):
1) Put the GCC binaries on a local disk, preferably on a SSD.
Do not put them on a CIFS mount - this gives terrible compilation times.
2) Use an older GCC version. GCC 3.x is way faster than 7.x.
3) Revisit the optimization options: -O is a good compromise, -O2 increases
the compilation times significantly, and -O2 -fexpensive-optimizations is
just excessive.
> > Bruno, do you mind if I add "time" to every multibuild target?
>
> Also, does the configure script have to support platforms without
> /usr/bin/time?
I do mind, yes. And you guessed the reason: We haven't tested portability.
The POSIX 'time' command produced ugly output. 'time' as a bash built-in is OK.
> I noticed that you use sed instead of tail
Yes: Solaris 10 'tail' does not understand the '-n' option.
See also the chapter "Portable Shell Programming" [1].
> so I wonder what the assumptions are.
The assumptions are those listed by the GNU coding standards [2].
Bruno
[1] https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Portable-Shell.html
[2] https://www.gnu.org/prep/standards/html_node/Utilities-in-Makefiles.html
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