This issue appears to be an upstream bug, since you tested the latest upstream kernel. Would it be possible for you to open an upstream bug report[0]? That will allow the upstream Developers to examine the issue, and may provide a quicker resolution to the bug.
Please follow the instructions on the wiki page[0]. The first step is to email the appropriate mailing list. If no response is received, then a bug may be opened on bugzilla.kernel.org. Once this bug is reported upstream, please add the tag: 'kernel-bug- reported-upstream'. [0] https://wiki.ubuntu.com/Bugs/Upstream/kernel -- 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/1531951 Title: A severe performance degradation while syncing md raid after the upgrade to 15.10 Status in linux package in Ubuntu: Triaged Bug description: I run Ubuntu from the fakerade (imsm) raid5 volume. If the volume is syncing, the system response is severely degraded. There is no problem if I boot the same system from the previous kernel 3.19.0-32. Some numbers: [md125_resync] kernel thread CPU consumption: 94 per-mill compared to 10 in 3.19 kernel [md125_raid5] kernel thread CPU consumption: 243 per-mill compared to 86 in 3.19 kernel 1MB direct read from md array: 0.5s compared to 0.01s in 3.19 kernel 1MB direct read from md raid member: 2.2s compared to 0.02s in 3.19 kernel As a result, it's practically impossible to work in 4.2 kernel if md raid is syncing (even the boot takes several minutes here), whereas in 3.19 I don't feel any performance degradation at all, regardless the raid volume is syncing or not. ProblemType: Bug DistroRelease: Ubuntu 15.10 Package: linux-image-4.2.0-22-generic 4.2.0-22.27 ProcVersionSignature: Ubuntu 4.2.0-22.27-generic 4.2.6 Uname: Linux 4.2.0-22-generic x86_64 NonfreeKernelModules: nvidia ApportVersion: 2.19.1-0ubuntu5 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC1: palo 3869 F.... pulseaudio /dev/snd/pcmC0D0p: palo 3869 F...m pulseaudio /dev/snd/controlC0: palo 3869 F.... pulseaudio CurrentDesktop: Unity Date: Thu Jan 7 18:51:39 2016 HibernationDevice: RESUME=UUID=f9900a93-c16d-4cae-9098-194fdf3abbfe InstallationDate: Installed on 2011-09-16 (1574 days ago) InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1) MachineType: System manufacturer System Product Name ProcFB: 0 VESA VGA ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.2.0-22-generic root=/dev/mapper/vg00-lv_ubuntu_root ro init=/sbin/upstart RelatedPackageVersions: linux-restricted-modules-4.2.0-22-generic N/A linux-backports-modules-4.2.0-22-generic N/A linux-firmware 1.149.3 RfKill: SourcePackage: linux UpgradeStatus: Upgraded to wily on 2016-01-02 (4 days ago) dmi.bios.date: 02/23/2009 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: 2102 dmi.board.asset.tag: To Be Filled By O.E.M. dmi.board.name: P5Q-PRO dmi.board.vendor: ASUSTeK Computer INC. dmi.board.version: Rev 1.xx dmi.chassis.asset.tag: Asset-1234567890 dmi.chassis.type: 3 dmi.chassis.vendor: Chassis Manufacture dmi.chassis.version: Chassis Version dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2102:bd02/23/2009:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnP5Q-PRO:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion: dmi.product.name: System Product Name dmi.product.version: System Version dmi.sys.vendor: System manufacturer To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1531951/+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
