swapping, performance, and distro choice
Posted: 17. Jan 2013, 05:15
So I'm just testing PCLinuxOS 2012.12 on my laptop. I am not particularly fond of it, or of the distro in general, but I must acknowledge that it is very very fast.
Part of that I guess is due to the BFS kernel. And part of it is undoubtedly due to KDE having a lot of stuff disabled. But I've noticed a broader pattern, which I think comes into play here. Some distros are a lot slower than others, in a very obvious, describable way: they're more swappy, even with the same vm.swappiness setting.
On Slackware, Debian, CentOS, and PCLOS (and their descendents): swapping only occurs under significant load. If you have 2+ GB of RAM then you will not see your OS start swapping, unless you start playing 3D games or copying huge files or something.
On Ubuntu, OpenSUSE, Fedora, and Mandriva/Mageia: swapping starts soon after you log in. Package management in particular causes lots of swapping, but even having too many browser tabs open will start eating into swap space; and performance is correspondingly bad. Furthermore, reducing the vm.swappiness sysctl reduces swapping only a little, if at all.
There is almost a pattern here. OpenSUSE, Fedora, and Mageia all use systemd, and therefore have to have the cgroup FS mounted... But Ubuntu doesn't. So I'm not sure exactly what's going on. Also, Arch Linux uses systemd now, and doesn't seem to suffer from particularly bad performance.
I'm kind of perplexed. My suspicion is that this has something to do with the way desktops are set up, because while Ubuntu (and Kubuntu, and Xubuntu) all swap a lot, customized Ubuntu installations (via the server or minimal install CD) work okay; and using e.g. Fluxbox on one of the offending distros, instead of the default desktop choice, nullifies the problem. But I'm not sure what services, or whatever, would be responsible for causing unneeded swapping.
Has anyone else observed this? What do you people think?
Part of that I guess is due to the BFS kernel. And part of it is undoubtedly due to KDE having a lot of stuff disabled. But I've noticed a broader pattern, which I think comes into play here. Some distros are a lot slower than others, in a very obvious, describable way: they're more swappy, even with the same vm.swappiness setting.
On Slackware, Debian, CentOS, and PCLOS (and their descendents): swapping only occurs under significant load. If you have 2+ GB of RAM then you will not see your OS start swapping, unless you start playing 3D games or copying huge files or something.
On Ubuntu, OpenSUSE, Fedora, and Mandriva/Mageia: swapping starts soon after you log in. Package management in particular causes lots of swapping, but even having too many browser tabs open will start eating into swap space; and performance is correspondingly bad. Furthermore, reducing the vm.swappiness sysctl reduces swapping only a little, if at all.
There is almost a pattern here. OpenSUSE, Fedora, and Mageia all use systemd, and therefore have to have the cgroup FS mounted... But Ubuntu doesn't. So I'm not sure exactly what's going on. Also, Arch Linux uses systemd now, and doesn't seem to suffer from particularly bad performance.
I'm kind of perplexed. My suspicion is that this has something to do with the way desktops are set up, because while Ubuntu (and Kubuntu, and Xubuntu) all swap a lot, customized Ubuntu installations (via the server or minimal install CD) work okay; and using e.g. Fluxbox on one of the offending distros, instead of the default desktop choice, nullifies the problem. But I'm not sure what services, or whatever, would be responsible for causing unneeded swapping.
Has anyone else observed this? What do you people think?