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

[Pandu Poluan]

On Dec 19, 2011 7:20 AM, "Dale" <rdalek1967@×××××.com> wrote:
>
> Walter Dnes wrote:
>>
>> It's probably the sum total of the effect of all the flags. I've renamed
the thread, to be more accurate. Here's how things went... * right after
the install (presumably with generic i686 code) the PC could not handle
streaming 1080i video from my HDHomerun TV tuner * I misinterpreted output
from gcc diagnostics, and concluded that "march=-native" left several flags
disabled that shouldn't be * acting on that (mis)information), I emerged
system+world+kernel and found that not only could my system handle 1080i,
it could handle a 1080p Youtube clip without problems, after a lot of
buffering. My 5 megabit ADSL connection was the limiting factor there. It's
supposed to be upgraded to 6 megabits one of these days, for some minor
improvement. * I mistakenly thought that it was the additional flags in
CFLAGS during the emerge system+world that boosted the video. Actually, the
emerge would've done the trick. The lesson from this is that, before doing
any benchmarking or heavy-duty usage, one should emerge system+world, to
replace the generic code from the install CD with fully optimized code.
It's easiest to so right after the initial install, so that there are as
few packages to emerge as possible.
>
>
>
> That is good advice too.  When I do a install, I unpack the tarball and
do the normal things and get my make.conf settings done.  Since there is
very little installed anyway, I do a emerge -ev world.  It usually takes
only a hour or so depending on the speed of the rig.  Thing is, you then
have everything compiled with your settings and not the generic ones the
tarball had.  It also updates anything that needs it too.  Even before
amd64 came along I did it this way.  Lots of people use Intel CPUs but I
use AMD.  I don't know what the person that made the tarball uses but
either way, he has to make it generic so that it will run on ANY CPU.
>
> I wonder if they should mention this in the docs?  It seemed to have made
a difference in your case for sure.  You went from not being able to play a
video to being able to play a HD video.
>

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,