From: Mauricio Fernandez <mfp@...>
Date: 2006-08-18T07:53:29+09:00
Subject: Re: Percentage of time spent in method dispatch?

On Fri, Aug 18, 2006 at 06:05:12AM +0900, John Lam wrote:
> I was wondering if anyone had taken a look at what % of time that ruby
> spends doing method dispatch?
> 
> I'll eventually do the experiments myself, but I wanted to check with
> y'all to see if someone had already done some investigations. It would
> be an interesting experiment to see how much you can improve method
> dispatch performance by caching the reference to the method call
> target, and invalidating it when the call context changes.

The current implementation has a method cache whose hit rate is above 95% or
so (don't remember the exact figure; it's not hard to reproduce anyway) ---
full method lookups are relatively rare.

Method dispatching is still fairly slow, though; I once measured that it took
some ~200 instructions to run a CFUNC, and about half as much with YARV.
Last time I read YARV's sources, it didn't have inline method caches (but it
was caching constants, IIRC), but it's been a while and they might have been
implemented meanwhile.

-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby