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[mm <1518457@xxxxxxxxxxxxxxxxxx>]

I really tried hard DD'ing and filling up RAM but I really can not
reproduce the issue under Ubuntu 15.04 on AWS EC2 nano. On my home
server boxes that issue also didn't appear on Ubuntu 15.04 either - so I
really think it was introduced between 15.04 and 15.10.

Linux ip-172-31-7-84 3.19.0-20-generic #20-Ubuntu SMP Fri May 29
10:10:47 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

root@ip-172-31-7-84:/home/ubuntu# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=15.04
DISTRIB_CODENAME=vivid
DISTRIB_DESCRIPTION="Ubuntu 15.04"


top - 19:17:38 up 45 min,  2 users,  load average: 3.52, 2.91, 1.93
Tasks:  87 total,   3 running,  84 sleeping,   0 stopped,   0 zombie
%Cpu(s): 36.4 us, 13.3 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si, 50.3 st
KiB Mem:    499128 total,   492924 used,     6204 free,     8552 buffers
KiB Swap:  1048572 total,    18664 used,  1029908 free.   136340 cached Mem

  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
11405 root      20   0  127120 124140   1360 R 36.6 24.9   3:19.84 memtester
11425 root      20   0  168080 165052   1340 R 36.0 33.1   3:09.11 memtester
11797 root      20   0    7012   2724   1660 D 16.6  0.5   0:54.64 dd
12110 root      20   0    7012   2792   1728 D  7.7  0.6   0:01.19 dd
 1190 root      20   0       0      0      0 D  2.0  0.0   0:00.98 kworker/u30+
   32 root      20   0       0      0      0 S  1.0  0.0   0:01.62 kswapd0
    1 root      20   0   35032   2020   1476 S  0.0  0.4   0:01.68 systemd
    2 root      20   0       0      0      0 S  0.0  0.0   0:00.00 kthreadd
    3 root      20   0       0      0      0 S  0.0  0.0   0:00.00 ksoftirqd/0
    5 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 kworker/0:0H
    7 root      20   0       0      0      0 S  0.0  0.0   0:00.67 rcu_sched
    8 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcu_bh

[...]


Total DISK READ :       3.88 K/s | Total DISK WRITE :      67.48 M/s
Actual DISK READ:       3.88 K/s | Actual DISK WRITE:      65.99 M/s
  TID  PRIO  USER     DISK READ DISK WRITE>  SWAPIN      IO    COMMAND
12110 be/4 root        0.00 B/s   67.48 M/s  0.00 % 86.28 % dd if=/de~0096 bs=1M
    1 be/4 root        0.00 B/s    0.00 B/s  0.00 %  0.00 % init
    2 be/4 root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [kthreadd]
    3 be/4 root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [ksoftirqd/0]
    5 be/0 root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [kworker/0:0H]
    7 be/4 root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_sched]
    8 be/4 root        0.00 B/s    0.00 B/s  0.00 %  0.00 % [rcu_bh]

[...]

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https://bugs.launchpad.net/bugs/1518457

Title:
  kswapd0 100% CPU usage

Status in linux package in Ubuntu:
  In Progress

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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