no swap makes system slower - why?

Felipe Figueiredo philsf79 at gmail.com
Sun Nov 4 10:08:23 UTC 2007


Hello,

before the question, a little background.

Since upgrade to gutsy, I found the overal performance much better than 
feisty, especially when opening the panel menus, add/remove programs, 
synaptic (loads faster), and else. Of course, desktop effects is a plus, but 
my PIM of choice - KDE's was incredibly s-l-o-w to load. I also had some 
firefox crashes that seemed unrelated, until I found kernel oopses in 
kern.log pointing to several background programs randomly crashing due to low 
RAM (and I thought 1GB was more than enough).

Then I discorved why: swap partition was off, as well as my /boot (I use LVM 
here). Grub was reading the partition as it should, and I could access it 
with a bootcd, which told me I didn't have a corrupt filesystem (i fsck'ed, 
nevertheless).

Ok, simple matter of activating both swap and the /boot partitions manually, 
right? Wrong - all I got was a non informative error:

philsf at peralta:~$ export LC_ALL=en_US
philsf at peralta:~$ sudo swapon -a
swapon: /dev/sda3: Invalid argument
philsf at peralta:~$ sudo swapon /dev/sda3
swapon: /dev/sda3: Invalid argument
philsf at peralta:~$ sudo mkswap /dev/sda3
/dev/sda3: Device or resource busy

The same went for the /boot partition. Nothing had appeared anywhere 
in /var/log.

After banging a little (ok, a lot), I found out that I have now installed the 
evms package. I honestly don't remember installing it, and don't know wether 
it got in in the upgrade, of before, but I now just have to 
use /dev/evms/sda3 instead, and my swap works great. IIRC, I didn't have to 
worry about evms changing location of usable devices since the upgrade from 
dapper to edgy.

I tried /etc/init.d/evms stop, but it didn't disable it enough so I could 
mount the devices using their normal names. I'll try disabling it in the rc 
dir, and rebooting, but am already fearing the worst. Maybe it's best to just 
leave the working thing alone?

Questions: 
1- Since swap access is slow (disk) compared to real RAM, I would expect that 
a swapless setup to be faster.

2- Is there an upgrade log, anywhere in /var, I could check if evms was 
installed before or during the upgrade?

3- Is there a way do completely (and safely) disable evms and restore my 
devices to their default locations?

regards
FF




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