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On Sun, Dec 18, 2011 at 12:45:27PM +0200, Nikos Chantziaras wrote |
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> |
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> On 12/18/2011 12:34 PM, Walter Dnes wrote: |
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> > |
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> > This was only recently installed. Is it possible that the generic x86 |
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> > code from the initial install was the problem? And that emerging |
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> > system+world got me full optimization? |
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> |
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> Could be. It could also be it's because of "-mfpmath=sse". That's only |
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> used by default on 64-bit. On 32-bit, the FPU is used for floating |
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> point operations by default, which gives better precision (80 bit vs 64 |
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> bit) but slower speed. |
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> |
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> But then again, that sounds too much of a performance difference. So if |
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> I had to guess, I'd say it's because of the world rebuild that made sure |
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> everything was built with proper optimizations. |
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It's probably the sum total of the effect of all the flags. I've |
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renamed the thread, to be more accurate. Here's how things went... |
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* right after the install (presumably with generic i686 code) the PC |
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could not handle streaming 1080i video from my HDHomerun TV tuner |
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|
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* I misinterpreted output from gcc diagnostics, and concluded that |
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"march=-native" left several flags disabled that shouldn't be |
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* acting on that (mis)information), I emerged system+world+kernel and |
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found that not only could my system handle 1080i, it could handle a |
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1080p Youtube clip without problems, after a lot of buffering. My 5 |
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megabit ADSL connection was the limiting factor there. It's supposed |
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to be upgraded to 6 megabits one of these days, for some minor |
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improvement. |
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* I mistakenly thought that it was the additional flags in CFLAGS during |
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the emerge system+world that boosted the video. Actually, the emerge |
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would've done the trick. |
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The lesson from this is that, before doing any benchmarking or |
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heavy-duty usage, one should emerge system+world, to replace the generic |
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code from the install CD with fully optimized code. It's easiest to so |
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right after the initial install, so that there are as few packages to |
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emerge as possible. |
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|
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-- |
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Walter Dnes <waltdnes@××××××××.org> |
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