I tested the upstream v4.18-rc2 kernel, and found the problem has been fixed.
Bisecting revealed https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5a8361f7ecceaed64b4064000d16cb703462be49 fixed the issue, which is included in v4.16.0. Given that the most recent Ubuntu kernel seems to be v4.15.y, when can I expect that commit to be included in an Ubuntu kernel release? Would the soonest likely be when 18.10 is released? -- 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/1779305 Title: Sluggish performance as Xen dom0 Status in linux package in Ubuntu: Confirmed Status in linux-signed-hwe-edge package in Ubuntu: New Bug description: 1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu 16.04 LTS 2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center Tried booting various versions between the 4.13.0-lowlatency and 4.15.0-lowlatency versions. Can confirm the problem appears on all 4.15.0 versions (e.g., 4.15.0-13), but is not present on any 4.13.0 version (e.g., 4.13.0-45). The version of Xen used is 4.9.0-0ubuntu3. I believe this isn't in Xenial's repositories, but actually from a later Ubuntu release, since I wanted some features of Xen that weren't in Xenial's version. Bisecting the commits narrowed down to the issue appearing after http://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/commit/?h=hwe- edge&id=a62a7117d91ca83d319566cbe16039f4e9f413c2 was committed. In fact, after recompiling and running the latest hwe-edge kernel (4.15.0-23) with that commit reverted, the problem disappears. This kernel is attached. I also intend to test the mainline kernel, but I haven't gotten around to it yet 3/4) What you expected to happen/What happened instead The newer kernel to not be significantly slower than the older kernel (I'm aware of Meltdown/Spectre mitigations causing slowdowns, but it should not be *this* much slower). Specifically, after upgrading to a 4.15.0 kernel from 4.13.0, I noticed these behaviours: - Time to log in via lightdm seems to have doubled in time or more (I did not actually time it, but it is taking significantly longer) - Scrolling in the Processes tab of system-monitor is noticeably choppy and laggy - The "user experience" in general seems to be laggy - Running a game in a Windows domU (with passthrough GPU) resulted in ~25% of the original FPS Interestingly, if I boot on bare metal (i.e., without Xen), the problem does not manifest. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: linux-image-4.15.0-22-lowlatency 4.15.0-22.24~16.04.1 ProcVersionSignature: Ubuntu 4.15.0-23.25~16.04.1-lowlatency 4.15.18 Uname: Linux 4.15.0-23-lowlatency x86_64 ApportVersion: 2.20.1-0ubuntu2.18 Architecture: amd64 CurrentDesktop: GNOME-Flashback:Unity Date: Fri Jun 29 21:46:35 2018 SourcePackage: linux-signed-hwe-edge UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1779305/+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
