[clue-tech] Swapped memory with 1GB of RAM?

[Nate Duehr]

Alex Young wrote:

>I've got a memory problem, and I'm stumped.
>
>I have a webserver (RH 9.0) running 2.4.20-19.9smp, and after a few
>days of uptime it gets ungodly slow at serving pages due to swapping. 
>   The machine has a gig of ram and is not running x or anything like
>that.
>  
>
I would ditto someone else's remarks about RH9's stock kernels and VM 
problems.  2.4.20 was around the time I also went through that pain.  I 
ran some Compaq servers that acted very badly with 1G of RAM, with 
Apache/Tomcat/MySQL and were actually better performers with 512MB RAM 
on identical hardware around the time of RH9.

I don't know what kernel you're on, but you may want to look and see if 
newer stuff is available via the Fedora Legacy Project  for RH9 since 
they're the only people doing updated "semi-official" RPM's for it, or 
compile your own from vanilla.  (Vanilla can be hard on RH machines, 
they add a lot of junk to their kernels you will probably need/want.)  
If you go vanilla, make sure you grab the source package for whatever 
you're using now and get the standard .config file so you can try as 
best as possible to compare apples to apples.

In later kernels, the BIGMEM options are available, and 2.6 has a 
complete VM rewrite basically -- but 1G is a weird break-point for all 
the new options... you can run the regular memory settings or you can 
jump to the 1G-4G mode.  Definitely Google for information about how to 
get to 2.6 from 2.4 if you've never done it.  Distros all kinda made the 
same decisions to jump to devfs and some other new features when 2.6 
came out... to take your 2.4 machine and plop a stock 2.6 kernel on it 
from the same or similar distro will probably leave it hideously broken.

Haven't ever seen anyone benchmark the difference between the two 
different kernel settings right at the 1G mark.

If you can jump to Fedora Core 3, the 2.6 kernels in there seem to do 
fairly well, but I can't compare to the old Apache/Tomcat machines 
because I don't work there anymore.  I know that's probably a painful 
proposition as upgrades from RH9 to Fedora I'm guessing probably aren't 
clean at all... (truthfully no production RH upgrade I ever did ever 
seemed to 100% work out right, and I always reinstall RH/Fedora machines 
after double-checking that I have backups of everything vs. using 
Anaconda and their crappy upgrades).

I also went through some pain along these lines (VM's at 1G) on Debian 
Sarge, but they cleared up pretty quickly.  The Gentoo laptop with 1G 
RAM also seems to scream, but I never ever recommend Gentoo for 
production systems.

Nate