apport information ** Tags added: apport-collected
** Description changed: On the UEC images on Amazon, from time to time people see hung task for more than 120 seconds messages. From previous experience with Amazon, EXT4 file systems are prone to these messages due to the way that the virtual (/dev/xvd*) EBS disks are presented to the DomU and EXT4's delayed commits. EBS volumes are presented to DomU's as physical disks that are attached in Dom0; the actual disk is a network device. During periods of high I/O, flushing of dirty pages can result in the hung tasks while the flushing to the network disk happens. Generally, this affects m2.* and cc1.4xlarge instance types (the expensive premium instances). Adjusting these the "vm.dirty_background_ratio" and "vm.dirty_expire_centisec" have show the ability to mitigate these symptoms. The problem, however, is that adjusting these values can result in poor system performance depending on the workload and the instance type. For example, on a m2.4xlarge which has 72G of RAM, the number of dirty pages can be significantly bigger than a t1.micro which only has 604M of RAM. This bug has been filed to see about getting guidance for the community from the kernel team on tuning of vm.dirty* settings to prevent hung tasks. vm.dirty_background_ratio = 10 vm.dirty_background_bytes = 0 vm.dirty_ratio = 20 vm.dirty_bytes = 0 vm.dirty_writeback_centisecs = 500 vm.dirty_expire_centisecs = 3000 vm.drop_caches = 0 --- ProblemType: Bug DistroRelease: Ubuntu 11.04 Package: linux-image-virtual 2.6.38.8.22 ProcVersionSignature: User Name 2.6.38-8.42-virtual 2.6.38.2 Uname: Linux 2.6.38-8-virtual x86_64 AlsaDevices: total 0 crw------- 1 root root 116, 1 2011-07-06 21:41 seq crw------- 1 root root 116, 33 2011-07-06 21:41 timer AplayDevices: Error: [Errno 2] No such file or directory Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory CurrentDmesg: [ 21.600011] eth0: no IPv6 routers present Date: Mon Jul 11 16:01:31 2011 Ec2AMI: ami-6463980d Ec2AMIManifest: (unknown) Ec2AvailabilityZone: us-east-1d Ec2InstanceType: t1.micro Ec2Kernel: aki-427d952b Ec2Ramdisk: unavailable Lspci: Lsusb: Error: command ['lsusb'] failed with exit code 1: ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: root=LABEL=uec-rootfs ro console=hvc0 ProcModules: acpiphp 24097 0 - Live 0x0000000000000000 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh insta + --- + AlsaDevices: + total 0 + crw------- 1 root root 116, 1 2011-07-25 20:32 seq + crw------- 1 root root 116, 33 2011-07-25 20:32 timer + AplayDevices: Error: [Errno 2] No such file or directory + Architecture: amd64 + ArecordDevices: Error: [Errno 2] No such file or directory + CurrentDmesg: + + DistroRelease: Ubuntu 11.04 + Ec2AMI: ami-c55b9cac + Ec2AMIManifest: (unknown) + Ec2AvailabilityZone: us-east-1a + Ec2InstanceType: t1.micro + Ec2Kernel: aki-427d952b + Ec2Ramdisk: unavailable + Lspci: + + Lsusb: Error: command ['lsusb'] failed with exit code 1: + Package: linux (not installed) + ProcEnviron: + LANG=en_US.UTF-8 + SHELL=/bin/bash + ProcKernelCmdLine: root=LABEL=uec-rootfs ro console=hvc0 + ProcModules: acpiphp 24097 0 - Live 0x0000000000000000 + ProcVersionSignature: User Name 2.6.38-10.46-virtual 2.6.38.7 + Tags: natty ec2-images + Uname: Linux 2.6.38-10-virtual x86_64 + UpgradeStatus: No upgrade log present (probably fresh install) + UserGroups: adm admin audio cdrom dialout dip floppy plugdev video ** Attachment added: "BootDmesg.txt" https://bugs.launchpad.net/bugs/808872/+attachment/2232166/+files/BootDmesg.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/808872 Title: Hung tasks on UEC cloud images with EBS volumes To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/808872/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
