no swap makes system slower - why?

[Jef Driesen]

Felipe Figueiredo wrote:
> 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?

I had a very similar problem after upgrading to Gutsy [1]. I don't think 
it is related to having evms installed, because I think I do not have it 
installed on my system (but I'm not 100% sure about that and I can't 
check it right now because I'm on a different machine now).

[1] https://lists.ubuntu.com/archives/ubuntu-users/2007-October/125957.html