From: John Carter <john.carter@...>
Date: 2008-01-17T12:04:29+09:00
Subject: Re: any tricks to speed up ruby? -fwhole-program?

On Wed, 16 Jan 2008, M. Edward (Ed) Borasky wrote:

> It's an interesting thought. However, I wasn't able to get gcc 4.2.2 to do 
> some simpler things, like profile-based optimization, on the Ruby source, so 
> I wouldn't expect something that complex to work out of the box. There are a 
> lot of great things in gcc, but not many of them are as well tested as, say, 
> the standard modular C library or program, and, of course, the Linux kernel.

I'm not sure thats simpler... I also looked at that once and decided
there were some distinctly unsimple things going on.

If I'm right about kde, then yes, its a very well tested feature. Also
there would be major impetus from embedded systems users to use whole
program optimization features.

> As far as I know, "-O3 -march=<your processor type>" is about the best you 
> can get out of gcc without a *lot* of work.

In the "medium work" category I suspect there are things relating to
function attributes and builtins that could get 5% or so more juice
(but tend to clutter the code with unportable improvements).

> And there are a lot more things you can do at the Ruby source level
> that have a bigger payoff than that does.

As always. My 100-10-1 rule of thumb is to expect speed up factors of up
to about 100x for using a much better algorithm, factors up to about
10x for code tweaks, factors up to 2x but usually near 1x for compiler
optimization tweaks.


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