F 15. 64 bit versus 32 bit.

[Jerry Feldman]

On 05/24/2011 04:44 PM, Fernando Cassia wrote:
> On Tue, May 24, 2011 at 17:40, Jerry Feldman <gaf at blu.org> wrote:
>> The bottom line here is you can't make a blanket statement
>> that 64-bit code is slower. And if you have a decent optimizing
>> compiler, your performance could improve.
> I don´t make any blanket statement. Sun/Oracle´s FAQ does say there´s
> a 0-15% performance hit due to bigger code.
> You´re right, there are other very valid reasons to use 64-bit code
> and 64-bit VMs.
>
> But in some instances 32-bit VMs are faster.
> FC
Are they talking about Sparc 64 or x86_64. You also have to look at a
number of things. I have been using Oracle 11g and I have not seen that
in a FAQ. On the Alpha one of the issues we had was the loading of
applications because a 64-bit app is certainly going to be bigger, but
there are many ways to mitigate this. We found on IA64 that my current
company's code ran slower on the IA64, but after much profiling we found
it was the branching and the IA64 architecture, not the 64-bits.

My statement is:
64-bit operating systems on X86-64 are faster than the same OS in 32-bits.

Some 32-bit applications will run faster than if they were 64-bit, but
some 64-bit applications run faster than their 32-bit versions.

Going back the the OP. For the most part you are better off with a
64-bit operating system. If you are going to run a VM, then most guest
(x86/x86-64) OSs will run mostly on the hardware, where if you want to
run a 64-bit guest on a 32-bit platform, you will be 100% emulation.

linux, and especially Fedora, does very well in a 64-bit environment,
and the Linux kernel has been 64-bit since 1994. Today, there are very
few reasons not to run a 64-bit OS on X86-64 platform.


-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
PGP key id: 537C5846
PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB  CA3B 4607 4319 537C 5846


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