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[Bug 1518457] Re: kswapd0 100% CPU usage
I've found that how easy it is to reproduce varies somewhat - some
versions it's triggered at almost any file manipulation, others I've had
to copy a couple of large files around at the same time or otherwise
increase disk access while moving large files - but I can reproduce it
absolutely consistently in the versions listed above. I've noticed that
in the affected versions I get large kswapd0 CPU usage spikes while
copying files around even if it doesn't always get stuck at 100% usage
indefinitely (though I can always get it to do that with sufficient
provocation), while unaffected versions kswapd0 hardly shows up in CPU
usage no matter what I do.
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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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