MailScanner on RHEL 3.2 AMD64

[Matt Kettler]

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Julian Field wrote:

> As it is written in Perl, this isn't hugely relevant. There are 64-bit
> builds of Perl, but fundamentally the Perl compiler is a 32-bit program.
> Also there are only 32-bit virus scanners.
> 
> I have MailScanner running on an AMD64 system, and it doesn't run much
> faster than on a 32-bit Xeon system.
>

unless you've got more than 4gigs of physical ram, that's largely what I would
expect.

unlike bus widths, doubling the processor register size doesn't double data
thruput, unless your numeric format is larger than the old register size. 64-bit
ints are used, mostly for things like file offsets, and Windows uses it for
timestamps, but they aren't so pervasive as to be a large percentage of CPU time
on a typical machine. (note: scientific simulations, CAD stations, etc could be
a large exception to this depending on the application. But most of those use
SIMD processor extensions for much their math anyway. Certainly MailScanner
isn't in this class.)

Your big benefit performance wise is being able to address >4 gigs of ram
without using PAE, but that's irrelevant on a box with 4 gigs or less. Unless
you're doing big-memory, don't sweat using a 32bit kernel on an AMD 64bit CPU.

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