HVM instance would have the same issue when using PV network drivers (which usually they do for performance). However one also needs to cause fragmented skbs which contain multiple compound page fragments. And that depends on many factors which may not always be easy to meet.
By now, there actually seems to be a work-around that has been applied to upstream v3.17. Looks like we have to pick the following (or actually get it into the stable process): commit 97a6d1bb2b658ac85ed88205ccd1ab809899884d Author: Zoltan Kiss <zoltan.k...@citrix.com> Date: Mon Aug 11 18:32:23 2014 +0100 xen-netfront: Fix handling packets on compound pages with skb_linearize ** Also affects: linux (Ubuntu Utopic) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Trusty) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Trusty) Importance: Undecided => Medium ** Changed in: linux (Ubuntu Trusty) Status: New => Triaged ** Changed in: linux (Ubuntu Utopic) Importance: Undecided => Medium ** Changed in: linux (Ubuntu Utopic) Status: New => Triaged ** Description changed: Running Ubuntu 14.04 LTS on EC2, we see a lot of the following in the kernel log: - xen_netfront: xennet: skb rides the rocket: 19 slots + xen_netfront: xennet: skb rides the rocket: 19 slots Each of these messages corresponds to a dropped TX packet, and eventually causes our application's connections to break and timeout. The problem appears when network load increases. We have Node.js processes doing pubsub with a Redis server, and these are most visibly affected, showing frequent connection loss. The processes talk to each other using the private addresses EC2 allocates to the machines. Notably, the default MTU on the network interface seems to have gone up from 1500 on 13.10, to 9000 in 14.04 LTS. Reducing the MTU back to 1500 seems to drastically reduce dropped packets. (Can't say for certain if it completely eliminates the problem.) The machines we run are started from ami-896c96fe. ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: linux-image-3.13.0-24-generic 3.13.0-24.46 ProcVersionSignature: User Name 3.13.0-24.46-generic 3.13.9 Uname: Linux 3.13.0-24-generic x86_64 AlsaDevices: - total 0 - crw-rw---- 1 root audio 116, 1 May 9 09:01 seq - crw-rw---- 1 root audio 116, 33 May 9 09:01 timer + total 0 + crw-rw---- 1 root audio 116, 1 May 9 09:01 seq + crw-rw---- 1 root audio 116, 33 May 9 09:01 timer AplayDevices: Error: [Errno 2] No such file or directory: 'aplay' ApportVersion: 2.14.1-0ubuntu3 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord' AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: Error: [Errno 2] No such file or directory: 'iw' Date: Fri May 9 09:11:18 2014 Ec2AMI: ami-896c96fe Ec2AMIManifest: (unknown) Ec2AvailabilityZone: eu-west-1c Ec2InstanceType: c3.large Ec2Kernel: aki-52a34525 Ec2Ramdisk: unavailable IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig' Lspci: - + Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99 PciMultimedia: - + ProcFB: - + ProcKernelCmdLine: root=LABEL=cloudimg-rootfs ro console=hvc0 RelatedPackageVersions: - linux-restricted-modules-3.13.0-24-generic N/A - linux-backports-modules-3.13.0-24-generic N/A - linux-firmware N/A + linux-restricted-modules-3.13.0-24-generic N/A + linux-backports-modules-3.13.0-24-generic N/A + linux-firmware N/A RfKill: Error: [Errno 2] No such file or directory: 'rfkill' SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) - --- + --- AlsaDevices: - total 0 - crw-rw---- 1 root audio 116, 1 May 9 09:54 seq - crw-rw---- 1 root audio 116, 33 May 9 09:54 timer + total 0 + crw-rw---- 1 root audio 116, 1 May 9 09:54 seq + crw-rw---- 1 root audio 116, 33 May 9 09:54 timer AplayDevices: Error: [Errno 2] No such file or directory ApportVersion: 2.14.1-0ubuntu3 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: Error: [Errno 2] No such file or directory CurrentDmesg: [ 24.724129] init: plymouth-upstart-bridge main process ended, respawning DistroRelease: Ubuntu 14.04 Ec2AMI: ami-896c96fe Ec2AMIManifest: (unknown) Ec2AvailabilityZone: eu-west-1c Ec2InstanceType: c3.large Ec2Kernel: aki-52a34525 Ec2Ramdisk: unavailable IwConfig: Error: [Errno 2] No such file or directory Lspci: - + Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99 Package: linux (not installed) PciMultimedia: - + ProcFB: - + ProcKernelCmdLine: root=LABEL=cloudimg-rootfs ro console=hvc0 ProcVersionSignature: User Name 3.13.0-24.46-generic 3.13.9 RelatedPackageVersions: - linux-restricted-modules-3.13.0-24-generic N/A - linux-backports-modules-3.13.0-24-generic N/A - linux-firmware N/A + linux-restricted-modules-3.13.0-24-generic N/A + linux-backports-modules-3.13.0-24-generic N/A + linux-firmware N/A RfKill: Error: [Errno 2] No such file or directory Tags: trusty ec2-images Uname: Linux 3.13.0-24-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm audio cdrom dialout dip floppy netdev plugdev sudo video _MarkForUpload: True + + break-fix: - 97a6d1bb2b658ac85ed88205ccd1ab809899884d ** Tags added: kernel-bug-break-fix -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1317811 Title: Dropped packets on EC2, "xen_netfront: xennet: skb rides the rocket: x slots" To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1317811/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs