4 ms·

I'm surprised that the swap implementation (or distros swap configuration) is so bad on Linux. I have a fresh Ubuntu 20.10 desktop installation and a few times

by tored 6y ago

I'm surprised that the swap implementation (or distros swap configuration) is so bad on Linux. I have a fresh Ubuntu 20.10 desktop installation and a few times it has come to slow crawl where you can't do anything, can't escape to tty or ssh, reboot is basically the only option. I recently learned searching the internets that it was the swapfile configuration. My 16GB RAM machine got a 2GB swapfile from the default installation so I doubled it to 4GB, but today it almost got full again, luckily I was just about to close a big memory hog and that saved me. I have now increased the swapfile to 6GB. If Ubuntu is giving default installations 2GB of swapfile on 16GB of RAM, shouldn't this happen to lots of users quite frequently? How many users are technical enough to understand this and fix it? How can this be a good solution? I can't recall that I ever got in trouble on Windows because of the swapfile.

michael-ax 6y ago
I had zero problems without swap-files for a long time, thinking that 16gb was a lot of ram, and that i could manage. it wasn't and i couldn't. Now I run two swap partitions the size of physical memory on all machines. Turns out that after some weeks a good third of allocated ram lives in swap proving its usefulness .. and that its quick to turn the aux-swap partition into one for lvm snapshots and i suppose to act as part of the set to emulate'baloon files' too. tl;dr; bad defaults. go with the size of physical ram and get suspend/hibernate/hybrid working and tested too. use a 2nd ram-sized partition for snapshots/lvm and emergency space/lvm|zfs.
- tored 6y ago
  That explains it, I noticed that if my machine was on for a while a degradation in performance happened, it was probably the swapfile then too, especially when it only has 2GB to work with. Yes, I probably need to set my swapfile to 16GB, I'm also investigating the swappiness setting, default 60 for desktop.
MayeulC 6y ago
I often went into similar issues before upgrading my RAM. SysRq+F is your friend :) https://en.m.wikipedia.org/wiki/Magic_SysRq_key https://en.m.wikipedia.org/wiki/Magic_SysRq_key That manually triggers OOM kill, making your system responsive again at the risk of killing something it shouldn't. At some point, I was probably using it five times a day. It got better when I started using swap (easier to recover when both full). I really recommend zram.

by tored 6y ago

michael-ax 6y ago

I had zero problems without swap-files for a long time, thinking that 16gb was a lot of ram, and that i could manage. it wasn't and i couldn't. Now I run two swap partitions the size of physical memory on all machines. Turns out that after some weeks a good third of allocated ram lives in swap proving its usefulness .. and that its quick to turn the aux-swap partition into one for lvm snapshots and i suppose to act as part of the set to emulate'baloon files' too. tl;dr; bad defaults. go with the size of physical ram and get suspend/hibernate/hybrid working and tested too. use a 2nd ram-sized partition for snapshots/lvm and emergency space/lvm|zfs.

tored 6y ago
That explains it, I noticed that if my machine was on for a while a degradation in performance happened, it was probably the swapfile then too, especially when it only has 2GB to work with. Yes, I probably need to set my swapfile to 16GB, I'm also investigating the swappiness setting, default 60 for desktop.

MayeulC 6y ago

I often went into similar issues before upgrading my RAM. SysRq+F is your friend :) https://en.m.wikipedia.org/wiki/Magic_SysRq_key https://en.m.wikipedia.org/wiki/Magic_SysRq_key That manually triggers OOM kill, making your system responsive again at the risk of killing something it shouldn't. At some point, I was probably using it five times a day. It got better when I started using swap (easier to recover when both full). I really recommend zram.