Re: 64-bit vs 32-bit userspace/kernel benchmark? Was: Athlon 64 X2 cpuinfooddities

[Jeffrey Hundstad <jeffrey.hundstad@mnsu.edu>]

David Lang wrote:

> On Tue, 10 Jan 2006, Jeffrey Hundstad wrote:
>
>>
>>> On 1/10/06, Andi Kleen <ak@suse.de> wrote:
>>>
>>>> On Tuesday 10 January 2006 03:12, Jesper Juhl wrote:
>>>>
>> ...
>>
>>>> Ah - how legacy.
>>>>
>>>>
>>> Yeah, but since my distro of choice is 32bit only and I don't much
>>> feel like porting it myself or using an unofficial port (slamd64) I'm
>>> sticking with a 32bit userspace. And as long as userspace is pure
>>> 32bit there doesn't seem to be much point in building a 64bit kernel.
>>> And I only have 2GB of RAM, so I don't have a use for the larger 64bit
>>> address space.
>>> I also don't run any apps that do a lot of math on >32bit numbers, so
>>> there's not much gain there either.
>>> I guess I would bennefit from the extra GPR's, but then I would at the
>>> same time loose a bit by all pointers being 64bit - both lose some
>>> disk space due to larger binaries and I'd have increased memory use
>>> and less efficient L1/L2 cache use.
>>>
>>> I don't think there would actually be much gain for me in switching to
>>> a 64bit kernel with a 64bit userspace atm.
>>> But if I'm wrong I'd of course love to hear about it :)
>>>
>>>
>>
>> Has anyone done any actual benchmark tests that show 64-bit vs 32-bit 
>> environments/distributions with Athlon64 processors.  If so, I love 
>> to see the results.  I too elected to stick with 32-bit, using the 
>> same reasoning/guessing above.
>
>
> remember that benchmarks are all dependant on your workload, but on 
> some of my workloads (lots of fork-based network services) I've seen a 
> 50%+ increase by switching from a 32 bit to 64 bit kernel with 32 bit 
> userspace, and a further 50%+ increase by switching to a 64 bit 
> userspace.
>

Thanks for your response.  I'm prob. being stupid here... but does 
"increase" here mean faster or slower?

> remember that on amd64 systems 64 bit programs have access to twice as 
> many registers as 32 bit programs. This can be more of a win then the 
> extra pointer size is a loss.


If you've done other "standard" type of benchmarks between the two 
please post your results.  Also, is there a big hit by using a nearly 
pure 32-bit environment + the rare 64-bit program when needed?

-- 
Jeffrey Hundstad