Re: [gentoo-user] How to properly change CFLAGS ?

[Stefan G. Weichinger]

Richard Fish schrieb:
> On 8/21/06, Stefan G. Weichinger <lists@×××××.at> wrote:
>> Acer TM 634
>> P4-M 1.8GHz (cpu family : 15, model : 2)
>> 512 MB RAM
>> 30 GB 5200 rpm HDD
>
> It's all relative.  I have a 2.1Ghz Core Duo with 2G of RAM and a
> 160Gb HD, so *I* would consider your laptop, um, "underpowered".  :-)

Oh my .... ;)
So you see, it is even more important to choose the right flags with
such an outdated box ;-)

> But I also run with -Os.  The fact is that some things will run
> slightly faster at -Os than -O2, and some things will be slightly
> slower.  The same applies comparing -O3 to -O2, or -O3 to -Os; it all
> depends on what you are doing at the moment.
>
> So you should not assume that -O3 is faster for some random task just
> because it is "more optimized".  It simply makes different trade-offs
> than -O2 or -Os, and because of the way CPUs and caches work these
> days, those trade-offs may help or hurt a particular segment of code.
>
> FYI, in all of the tests I did, the performance was within 10% of the
> median. The real deciding factor for me now is that -Os seems to take
> much less time and memory to compile than -O2 or -O3.  And being a
> ~arch user, time-to-compile is a nice thing to reduce.


I am going the -Os-way now, using your script from your other posting.

Thanks a lot for the information,
Stefan
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