Re: [gentoo-user] USE="mmx mmxext sse sse2 ssse3 3dnow 3dnowext"

[Stroller <stroller@stellar.eclipse.co.uk>]

On 27 May 2009, at 11:00, Daniel Iliev wrote:
> ...
> I'm afraid the common sense says disabling the "cpudetection" USE
> flag could lead to the problem I described in my previous message.
> Please, don't get me wrong - I'm not arguing and I've never tried to
> build mplayer with EIS that is unsupported by the CPU. It may work if
> the build system detects and corrects such errors when cpudetection is
> disabled.

I think it shouldn't apply to mplayer, as explained by Volker earlier  
in the thread. If a USE for an unsupported EIS is detected, the  
mplayer build process will ignore it, and build without them. This is  
because mplayer specifically is particularly clever about this,  
apparently.

> I personally set the correct EIS USE flags for my CPU globally and
> disable the cpudetection flag.

Clearly this is the ideal way.

> ... I didn't suggest you this approach because I believe somewhere  
> in this
> thread you mentioned you wanted to use the same settings on several
> different systems.

Not necessarily, but I don't want to have to *think* too much about  
hardware. I mean, I can safely set MMX because I know reasonably well  
what it is, I remember when it came out, and I remember reading as the  
next couple of subsequent generations of CPU were released that they  
would continue to support it. I have a pretty good idea that MMX is  
ubiquitous, and I imagine it to be supported even to the very latest  
Intel CPUs (not sure about AMD?).

But I don't know what SSE is or SSSE (??) or any of the others, and I  
don't really have any desire to know. Just so long as my server works  
then I'm happy. I mean, I guess if I used Linux on the desktop then  
performance might be more important to me, and it would behove me to  
optimise each system. Or if my server carried a lot of load. But my  
Linux boxes mostly don't -  they sit in a corner & serve files by  
Samba & email by IMAP and very little more.

mplayer is kinda an exceptional case for me, because I rip DVDs  
to .mp4 format and then stream them across the network from the  
fileserver to my PS3. When I rip them, the process runs circa 12 or 14  
hours, so if I can shave 10% of this then that may be useful - the  
movie may be ready to watch an hour earlier, and on some occasion I  
may be glad of that.

So if I `flagedit media-video/mplayer mmx mmxext sse sse2 ssse3 3dnow  
3dnowext` that gets me the best performance for mplayer without having  
to think about it.

Of course, the amount of time I've spent on this thread, I could  
perhaps have learned *exactly* what all these extended instruction  
sets do, who designed them, whether they're cross-licensed between  
manufacturers and what their prospects are for continued support in  
the future. But I would personally find that very boring, and I am  
much happier to have learned a little about how mplayer's build system  
works and how Gentoo wraps that.

Stroller.