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

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