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[Bug 1518457] Re: kswapd0 100% CPU usage
A workaround that seems to work for me (and one that doesn't involve
dropping caches periodically) is to downgrade udev to 219-7ubuntu6 (as
suggested by Øystein above). On 15.10 wily, add vivid-updates to your
apt sources to be downgrade to this version of udev.
I noticed this bug is more likely to occur on servers with less memory /
more memory pressure. I was only able to reproduce it on our t2.micro
and t2.small instances on EC2, and using larger EC2 instances was our
first workaround. (In fact, after downgrading udev I was also downgrade
to smaller EC2 instances again.)
This bug also seems more likely to occur on servers with faster disk
I/O, given I was only able to reproduce it on instances with gp2 (SSD)
storage and not on standard (magnetic) storage on EC2.
Our use case is a bunch of EC2 instances all using the Ubuntu 15.10 wily
AMI, and currently running the latest 4.2.0-23-generic kernel.
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kswapd0 100% CPU usage
Status in linux package in Ubuntu:
As per bug 721896 and various others:
I'm on an AWS t2.micro instance (Xeon E5-2670, 991MiB of memory).
Occasionally (about once a day), kswapd0 falls into a busy loop and
spins on 100% CPU usage indefinitely. This can be provoked by
copying/writing large files (e.g. dding a 256MB file), but it happens
occasionally otherwise. System memory usage (not including
buffers/caches) currently sits at 36%, which is typical. Initially
I had no swap space configured; I've since tried enabling a 256MB swap
file, but the problem continues to occur and no swap space is used.
The system can be recovered with `echo 1 > /proc/sys/vm/drop_caches`.
Happy to provide further information/take further debugging actions.
 Full output from `free`:
total used free shared buffers cached
Mem: 1014936 483448 531488 28556 9756 112700
-/+ buffers/cache: 360992 653944
Swap: 262140 0 262140
DistroRelease: Ubuntu 15.10
Package: linux-image-4.2.0-18-generic 4.2.0-18.22
ProcVersionSignature: Ubuntu 4.2.0-18.22-generic 4.2.3
Uname: Linux 4.2.0-18-generic x86_64
crw-rw---- 1 root audio 116, 1 Nov 19 19:40 seq
crw-rw---- 1 root audio 116, 33 Nov 19 19:40 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
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:
Date: Fri Nov 20 20:44:30 2015
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99
MachineType: Xen HVM domU
PATH=(custom, no user)
ProcFB: 0 xen
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-18-generic root=UUID=35bc01f4-4602-4823-976e-508edef899df ro console=tty1 console=ttyS0 net.ifnames=0
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.product.name: HVM domU
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