Bug Description

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

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

ProcVersionSign ature: 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

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)

Ec2Availability Zone: 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

RelatedPackageV ersions:

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

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)

Ec2Availability Zone: 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

ProcVersionSign ature: User Name 3.13.0- 24.46-generic 3.13.9

RelatedPackageV ersions:

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: - 97a6d1bb2b658ac 85ed88205ccd1ab 809899884d

break-fix: - 11d3d2a16cc1f05 c6ece69a4392e99 efb85666a6