Spamassassin scanning slower on Linux compared to FreeBSD

[Julian Yap <ju...@gmail.com>]

I have common hardware being Dual AMD64 CPU's with 4GB of RAM.
Running Spamassassin 3.0.4 with exactly the same rules and setup.
Running between 7 and 15 child processes.

I'm finding that using FreeBSD 6.2 (64-bit kernel) is having much
faster scan times then any GNU/Linux system I've run.

Here is what I'm typically seeing
FreeBSD: 0.4-2 seconds an email
GNU/Linux: 2.5-10 seconds an email.  Occasional emails with ~20 second scans.

I've tested disabling Bayes (to rule that out) on the GNU/Linux system
but I can't get the same timings as with the FreeBSD systems.  Tested
on CentOS 4.4 and on Fedora 6 GNU/Linux systems.

Even the older FreeBSD systems running 5.x (and worse hardware) beat
the pants off the GNU/Linux systems.

Has anyone else encountered these similar issues and timings?  Is
GNU/Linux usually this slow?

- Julian

Re: Spamassassin scanning slower on Linux compared to FreeBSD

[Jason Haar <Ja...@trimble.co.nz>]

Julian Yap wrote:
> I'm finding that using FreeBSD 6.2 (64-bit kernel) is having much
> faster scan times then any GNU/Linux system I've run.
>
For such a large difference (0.4 vs 10) it has to be DNS related.

I'll take a stab: ipv6. If you have ipv6 enabled, Linux will attempt to
do ipv6 DNS lookups first - then the successful ipv4 ones.

Disable ipv6 (echo "alias net-pf-10 off" >> /etc/modprobe.conf &&
reboot) and see if the difference fades away

-- 
Cheers

Jason Haar
Information Security Manager, Trimble Navigation Ltd.
Phone: +64 3 9635 377 Fax: +64 3 9635 417
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