I've had the issue mostly when running with no swap. I added 1GB swap file and it fixed it on the machine with less memory usage, but the machine with the database (using more memory most of the time) still has the bug occur about once a day.

Ubuntu 16.04 for both, not happening on 14.04.

Sent from my iPhone

> On Jun 4, 2016, at 5:11 PM, Jonathan Vargas <email address hidden> wrote:
> 
> I face the same issue, running a t2.micro (1 GB) for a Nginx/Ruby
> application with really low demand. The kswapd0 process takes the CPU to
> 100% and the overall system performance is downgraded.
> 
> Linux server 4.4.0-22-generic #40-Ubuntu SMP Thu May 12 22:03:46 UTC
> 2016 x86_64 x86_64 x86_64 GNU/Linux
> 
> To reproduce it, I just create a 1GB file in the filesystem using "dd":
> 
> if=/dev/zero of=temp bs=1k count=1024k
> 
> I created a swap file to solve the issue but it continues. After
> dropping the page cache with:
> 
> echo 3 > /proc/sys/vm/drop_caches
> 
> the issue is solved temporarily.
> 
> 
> ** Attachment added: "Selection_320.png"
>   https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518457/+attachment/4677030/+files/Selection_320.png
> 
> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1518457
> 
> Title:
>  kswapd0 100% CPU usage
> 
> Status in Linux:
>  Unknown
> Status in linux package in Ubuntu:
>  Confirmed
> 
> Bug description:
>  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[1]. 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.
> 
> 
>  [1] 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
> 
>  ProblemType: Bug
>  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
>  AlsaDevices:
>   total 0
>   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'
>  ApportVersion: 2.19.1-0ubuntu5
>  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: N/A
>  Date: Fri Nov 20 20:44:30 2015
>  Ec2AMI: ami-1c552a76
>  Ec2AMIManifest: (unknown)
>  Ec2AvailabilityZone: us-east-1d
>  Ec2InstanceType: t2.micro
>  Ec2Kernel: unavailable
>  Ec2Ramdisk: unavailable
>  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
>  PciMultimedia:
> 
>  ProcEnviron:
>   TERM=screen
>   PATH=(custom, no user)
>   LANG=en_US.UTF-8
>   SHELL=/bin/bash
>  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
>  RelatedPackageVersions:
>   linux-restricted-modules-4.2.0-18-generic N/A
>   linux-backports-modules-4.2.0-18-generic  N/A
>   linux-firmware                            N/A
>  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
>  SourcePackage: linux
>  UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
>  UpgradeStatus: No upgrade log present (probably fresh install)
>  dmi.bios.date: 05/06/2015
>  dmi.bios.vendor: Xen
>  dmi.bios.version: 4.2.amazon
>  dmi.chassis.type: 1
>  dmi.chassis.vendor: Xen
>  dmi.modalias: dmi:bvnXen:bvr4.2.amazon:bd05/06/2015:svnXen:pnHVMdomU:pvr4.2.amazon:cvnXen:ct1:cvr:
>  dmi.product.name: HVM domU
>  dmi.product.version: 4.2.amazon
>  dmi.sys.vendor: Xen
> 
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