Re: [Xen-users] 32bit or 64bit dom0?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Jan 26, 2010 at 09:09:00AM -0800, Grant McWilliams wrote:
>        > Â  Â  Â -- Pasi
>        >
>        > Â  Â That depends one whether you consider (up to) 20% worth
>        considering! I'd
>        > Â  Â be willing to change for 5%.
>        >
>        > Â
>        Â [3][1]http://www.phoronix.com/scan.php?page=article&item=616&num=1
>        >
> 
>        Hmm.. did you paste wrong url? That url only has 32b vs. 64b?
> 
>        Here's 32b vs. 32b PAE benchmark:
>        [2]http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae
> 
>        Although that benchmark must have something wrong with the 32 vs 64
>        numbers..
>        the different can't be THAT big.
> 
>        "In the fourteen tests for this article we did not find using Ubuntu's
>        32-bit PAE kernel
>        to have a dramatic performance impact whether it be positive or
>        negative.
> 
>        Granted, we were using just 4GB of system memory that is common to
>        many desktops,
>        but if using 8GB, 16GB, or even a greater memory capacity the
>        performance
>        penalties are perhaps higher. "
>        -- Pasi
> 
>      Yes I did! Thanks. Here try this.
> 
>      [3]http://www.phoronix.com/scan.php?page=article&item=ubuntu_32_pae&num=1
>      Grant McWilliams
> 
>    I either posted two quick or too late! So the quote was saying that PAE
>    didn't have an impact over a stock 32 bit kernel
>    but if you compare it to the 64 bit kernel there's a serious hit. In the
>    tests they did the 64 bit kernel was faster by quite a bit
>    in every way. I've blindly been using 64 bit kernels wherever possible but
>    this helps me know that I've benefited from it.
> 

That "Apache Benchmark" must be wrong, THAT huge difference can't be true.

But yeah, in general 64b should be faster nowadays compared to 32b or 32b PAE, 
since it has a lot more registers to use etc..

32b vs 32b PAE doesn't seem to be big difference, at least not with 4 GB of RAM.
Also PAE gives you possibility to use NX protection..

-- Pasi


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