In my opinion I also agree to use deadline scheduler for server kernel which is also the same problem on the 4.15 kernel, if a server kernel would still exist.
Under trusty we generally saw good performance with deadline scheduler and on a recent SSD based deployment with 4.15 I noticed a large performance regression for random IO until we reverted to deadline. You could argue that the scheduler can be changed at any time but on the contrary I would assume more general suitable parameters from a server distro vs a desktop distro. My larger problem is that this change was seemingly done via https://kernel.ubuntu.com/git/ubuntu/ubuntu-zesty.git/commit/?id=af80b83a2b6184fea27f050948146fcd9a28070d by a test based on kernel compiles etc, which to be honest, is not a standard server use case. Apart from the issue that I could not spot any documentation on the release notes that this has changed. If this has been documented and simply missed it, then please ignore this comment. But now I'm wondering what else has changed now. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1008400 Title: Ubuntu server uses CFQ scheduler instead of deadline Status in linux package in Ubuntu: In Progress Bug description: Ubuntu server now uses the '-generic' kernel, as the '-server' kernel doesn't exist anymore. With this change the default server disk scheduler changed from deadline to CFQ. This is very bad for servers, deadline should absolutely be the default for servers. For example we moved some KVM images to an Ubuntu 12.04 server, but we had to revert as we got lots of disk errors and eventually frozen disks on these KVM's due to write timeouts. It took us a while before we found out that this 12.04 server used CFQ, which surprised us a lot. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1008400/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
