On optimizing Theora

Tiago Marques tiagomnm at gmail.com
Sun Feb 22 14:21:10 EST 2009


Can you please try both options with also the following
ones:*-ftree-vectorize -funroll-loops -m3dnow

Also, it may be a good idea to test both geode and i586 with *-m3dnow *and *
-mno3dnow*, since the compiler may be causing problems while vectorizing.
Another option is to test also with i486 compilations, as per what I had
already found in this thread:


Let me underscore my colleague's statement.  Do not use the 586 target.
In testing we've found that the 586 "optimized" version can be up to 3x
slower vs. the 386/486 versions on the Geode LX.

This should be due to Geode LX not being a superscalar processor (while the
i586 is) may be causing problems even with the i586 march.

Best regards,
                          Tiago Marques

On Fri, Feb 20, 2009 at 2:23 PM, Benjamin M. Schwartz <
bmschwar at fas.harvard.edu> wrote:

> Hash: SHA1
> Tomeu Vizoso wrote:
> > On Fri, Feb 20, 2009 at 06:41,  <quozl at laptop.org> wrote:
> >> On Fri, Feb 20, 2009 at 12:28:42AM -0500, Benjamin M. Schwartz wrote:
> >>> GCC 4.3 evidently does not do a very good job of optimizing for geode.
> >> What percentage of CPU time was spent in libtheora?
> 100%.  The encoder was operating in a continuous loop.
> > Yeah, both X and jffs2 seem to use a lot of cpu on the XO, so if they
> > were involved during your tests, you may have seen little of theora
> > itself.
> Neither X nor jffs2 was involved.  The input file (y4m or ogv) was cached
> in memory, and the output stream (ogv or y4m) was being sent directly to
> /dev/null, and not displayed.
> The only action being taken in X was to display, in the Terminal activity,
> a text-only progress bar, rendered by the encoder_example, or dump_video
> command.  These commands are part of libtheora, and were recompiled with
> it, so the point remains.
> - --Ben
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