Re: [Valgrind-users] Preliminary little speedup patch (seen 7% speedup)

[Christian L. <chr...@le...>]

On Tue, Mar 18, 2003 at 08:45:08AM +0000, Julian Seward wrote:

> The computed goto thing is useful for speeding up bytecode interpreters
> -- I've used it for that before now -- but this isn't such a case.  It's
> the switch in the x86 parser which switches on the opcodes being
> examined.  It is used only once per instruction which V translates and
> so the cost difference (a few host insns) must be completely swamped by
> the rest of the translation costs (000s of host insns per translated
> insn, typically).  And translation costs are usually small (0-15%)
> compared to the cost of running the translation.  

> So I'm mystified where
> the 7% speedup number comes from.

Yes, absolutly, it's very obscure.

Some little changes decresed the performance again, damn, I fooled
myself.

It could be some alignment effect.
So perhaps this stupid 7% are also only on athlon-xp's.

But I don't know how to analyse what function takes how long, than it
should be easy to find the function were this difference is.


Christian Leber

-- 
  "Omnis enim res, quae dando non deficit, dum habetur et non datur,
   nondum habetur, quomodo habenda est."       (Aurelius Augustinus)
  Translation: <http://gnuhh.org/work/fsf-europe/augustinus.html>