Page faults and threads

Alejandro Imass ait at
Wed Dec 8 18:05:13 UTC 2010

On Wed, Dec 8, 2010 at 12:27 PM, Mark Terribile <materribile at> wrote:


Copying the list for this comment...

Well I can tell you this much. A while back I carried out some heavy
load testing on a Catalyst app on mod_perl, mod_worker apache 2 on
FBSD 6.2 and Debian with kernel 2.6.18 both on 64 bits same exact

FreeBSD 6.2 Stable
Apache 2.2.3, Server MPM: Worker
mod_perl 2.0.4
Perl v5.8.8 built for amd64-freebsd-thread-multi
Catalyst 5.7014
mysql  Ver 14.12 Distrib 5.0.45, for portbld-freebsd6.2 (amd64) using  5.2

Debian 4.0 (Etch) Stable
Apache 2.2.3, Server MPM: Worker
mod_perl 2.0.4
Perl v5.8.8 built for amd64-debian-thread-multi
Catalyst 5.7014
mysql Ver 14.12 Distrib 5.0.45, for Debian (amd64) using 5.2

I can't disclose the official results, but the bottom line was that
Linux was generally somewhat faster (61 vs. 72 ms per request on
average) but it's over-optimistic memory broke the OS completely when
maxing out and consuming the swap, and we concluded that the VM in
that version of Linux was particularly broke for our application.
Coincidentally you could observe a dramatic difference in the Virtual
and Resident size of each Apache process when in peak load:

Linux 2.6.18 : 710/130
FreeBSD 6.2: 185/132

(it also proved in both cases that threaded mod_perl (an esoteric mix
in the eyes of many an expert) saved tons of RAM and was generally
very stable ;-))

Anyway what really caught our attention in these tests is that when
the extreme load was removed, FBSD recovered almost immediately like
nothing had happened and we had to reboot Linux almost every time,
cause it remained very unstable afterwards. We did manage to play with
Linux's vm settings especially the over-committal stuff to somewhat
behave like FBSD,  but vanilla FBSD was always more stable in every
test. This told us that the FBSD folks must be doing something right
in the standard thread / vm management in FBSD and we switched to it
since for our heavy-weight Web deployments.

> I'd like to know if things how things are now on FreeBSD.

Hopefully this thread will catch the eye of some FBSD threading experts !

>    Mark Terribile
> --- On Wed, 12/8/10, Alejandro Imass <ait at> wrote:
>> From: Alejandro Imass <ait at>
>> Subject: Re: Page faults and threads
>> To: "Mark Terribile" <materribile at>

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