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Re: gcc: poor log() performance on Intel x86_64
- From: Andrew Haley <aph at redhat dot com>
- To: Torsten Rohlfing <torsten at synapse dot sri dot com>
- Cc: gcc at gcc dot gnu dot org, libc-alpha at sourceware dot org
- Date: Wed, 15 Mar 2006 17:23:11 +0000
- Subject: Re: gcc: poor log() performance on Intel x86_64
- References: <4417332A.7050004@synapse.sri.com> <17431.62274.975333.80298@zapata.pink> <44184737.4010606@synapse.sri.com>
Torsten Rohlfing writes:
> Andrew Haley wrote:
>
> > > When I run the two binaries on the exact same box and time them, I get
> > > the following outputs:
> > >
> > > time ./testlog64
> > > 13.264u 0.000s 0:13.26 100.0% 0+0k 0+0io 0pf+0w
> > >
> > > time ./testlog32
> > > 6.960u 0.004s 0:06.96 100.0% 0+0k 0+0io 0pf+0w
> >
> >You have weird hardware.
> >
> >[aph@zorro ~]$ time ./testlog64
> >
> >real 0m7.330s
> >user 0m7.328s
> >sys 0m0.004s
> >[aph@zorro ~]$ time ./testlog32
> >
> >real 0m7.538s
> >user 0m7.528s
> >sys 0m0.000s
>
> So it's not a big brand box, but I didn't think of it as totally obscure
> either.
Mm yes, but the fact that I can't duplicate your problem suggests that
it might be localized to a particular CPU design of a perticular
library build. It's hard to be sure, but it's not a generic gcc
problem.
Andrew.