Improving the performance of OpenJDK
gbenson at redhat.com
Thu Feb 19 08:34:47 PST 2009
Gary Benson wrote:
> Gary Benson wrote:
> > > > > Edward Nevill wrote:
> > > > > > get_native_u2() and get_Java_u2() ... This seems to be a
> > > > > > misguided attempt of the original authors to optimised
> > > > > > reading of halfwords (judging by the comment immediate
> > > > > > preceding the code).
> > So I did a quick SPECjvm98 run of this change on amd64. A couple
> > of the times are improved, by 3-10%, but one of the times is
> > *slower* by 11%. See attached. I'm not sure what to make of
> > that...
> I'm wondering if rewriting get_Java_u2() to read directly rather
> than read and swap is speeding it up, but removing the optimization
> from get_native_u2() is slowing it down. I'm going to try this with
> the original get_native_u2() and with get_Java_u2() just a copy of
> the big-endian get_native_u2().
So this way around it's a little more encouraging; two of the times
are 8-10% faster, one is 5% faster. Some of the times are still
slower though, though not by as much, maybe 1-2%. It's still
disturbingly ambiguous though... thoughts?
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