Re: [gentoo-user] A tale of computing thud and blunder

[Paul Hartman <paul.hartman+gentoo@gmail.com>]

On Mon, Dec 19, 2011 at 12:15 AM, Dale <rdalek1967@gmail.com> wrote:
> Pandu Poluan wrote:
>>
>>
>> Kind of like what I always do when I switch from -march=nocona to
>> -march=native. (Usually I use -march=nocona to ensure seamless VM migration
>> on my XenServer-equipped boxen, but for some VMs, i.e., those requiring me
>> to wring out every last drop of performance, I go native.)
>>
>> That said, if you want to experience fully the "GCC Graphite"
>> optimizations, you'll also want to do emerge -ev ;-)
>>
>> Rgds,
>>
>
>
> Is Graphite worthwhile on a desktop system or is it better suited for
> servers or both?  I found this but still not sure what it is intended for:
>
> http://gcc.gnu.org/wiki/Graphite/4.5
>
> Are there any reasons to leave this be for a while?  You know, bugs or
> packages that don't work with it?

I used it for @world and ran into a couple times when things were
broken with it enabled... Don't really remember specifics. I didn't
notice any perceivable speed difference, so I stopped using it just to
simplify things in the future. :)

In general,I have changed my CFLAGS to be less aggressive over the
past years. I started with the most aggressive optimizations, and
using -march=whatever... At some point I researched compile times for
different optimizations and realized some packages were taking tens of
minutes longer to compile! Surely whatever potential speed increase of
-O3 vs -O2 was not going to give me tens of minutes cumulatively. If
there is a package that really benefits from some specific
optimization (and doesn't already set those flags itself in the
ebuild), I'll set the CFLAGS for that individual package but leave the
rest of world very simplistic.

Same with -march, I've gone to using -mtune instead, after having to
move hard drives into a system with different CPU feature set. And for
virtual machines (in hosts I don't control, especially), they could be
migrated to some other machine without my knowledge, and i don't want
it to stop working if that happens.