Re: confused about performance
M. Edward (Ed) Borasky wrote:
> >> On Wed, Jun 13, 2007 at 04:40:52PM -0600, Sebastian Kuzminsky wrote:
> >>> Hi folks, I just bought a pair of AMD64 systems for a work project,
> >>> and I'm confused about the performance I'm getting from them. Both are
> >>> identically configured Dell Dimension C521 systems, with Athlon 64 X2
> >>> 3800+ CPUs and 1 GB RAM.
> >>>
> >>> On one I installed using the Etch (4.0r0) i386 netinst CD, then
> >>> upgraded to Lenny. This one's running linux-image-2.6.21-1-686.
> >>>
> >>> On the other I installed using the current (as of 2007-06-13) Lenny d-i
> >>> amd64 snapshot netinst CD. This one's running
> >>> linux-image-2.6.21-1-amd64.
> >>>
> >>> The one with the x86 userspace and 686 kernel is faster than the one
> >>> with x86_64 userspace and amd64 kernel. The difference is consistently
> >>> a few percent in favor of x86 over x86_64.
> >>>
> >>> My only benchmark is compiling our internal source tree (mostly running
> >>> gcc, some g++, flex, bison, etc). We're using gcc-4.1 and g++-4.1.
> >>> I've tried it with a cold disk cache and hot disk cache, in both cases
> >>> x86 is faster than x86_64.
> >>>
> >>> I was expecting a win for 64 bit. What's going on here?
You've tried compiling with the jobs flag?
make -j[n]
Look here for more:
http://www.cmcrossroads.com/content/view/7483/268/
Or the code isn't optimized for x86-64
New docs are out a few days:
http://developer.amd.com/
> Well ...
>
> 1. 32-bit isn't going away. The new chips are all going to be
> 64-bit-capable (and virtualization-capable, multi-core, etc.) but the
> software is going to lag that.
>
> 2. There are two reasons you'd want a 64-bit machine:
>
> a. You have a production application that *needs* a 64-bit machine.
> For the moment, most but not all of those are high-performance
> scientific computing.
>
> b. You want to develop 64-bit applications
and interested on the NX bit for security.
(how the openBSD guys ;-)
c. You want a stable dual-, quad- or more Socket machine and dedicated Memory
to each Processor. NUMA
(maybe each Socket with a dual-, quad- or more Core Processor)
d. You love free software and want free hardware too.
AMD ist working together with the community from the beginning of AMD64
development and all specs about the Opteron and 8000er chipsets are open.
e. You are only mad about opteron :-)
- because manufactured in your county.
- AMD is helping the community with LinuxBIOS.
(Nearly all Tyan K8 Thunder's with 8000er chips can running it)
- Opteron's make more moo
...
Ciao Marco!
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