Public bug reported:

Hello,

I am experiencing a noticeable system slowdown since I upgraded from
Xenial to Yakkety on several VM under XenServer 6.5 (fully patched).

I understand it will be difficult for me to describe what is happening
and for you to troubleshoot this issue but I'll try to do my best.

Just after booting the machine is pretty responsive but after some time
it starts responding very slowly.

Bash autocompletion for file paths takes 1-2 seconds to respond,
commands as "host" take hundred of milliseconds consuming hundred of ms
of CPU. Compiling is an order of magnitude slower, etc.

I wasn't able to detect what is causing the slowness. I tried to strace
slow process with no evident cause. It does not seem to be something I/O
bound.

I ran "host" in an infinite loop causing 100% CPU usage seen from
XenServer, 100% CPU usage in top but the sum of CPU usage from the
processes is under 10%.

top - 00:51:48 up 1 day,  4:49,  3 users,  load average: 1.47, 1.02, 0.59
Tasks: 144 total,   2 running, 142 sleeping,   0 stopped,   0 zombie
%Cpu(s): 74.4 us, 24.4 sy,  0.0 ni,  1.1 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  4044600 total,  1719740 free,   843100 used,  1481760 buff/cache
KiB Swap:  2095100 total,  2095100 free,        0 used.  3139664 avail Mem 

  PID USER      PR  NI   VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND       
                                                   
30968 yggdra    20   0  13460    696    616 R  5.8  0.0   0:00.18 host          
                                                   
28790 root      20   0  42020   3748   3104 R  0.6  0.1   0:02.47 top   
[...]


I downgraded to the last Xenial kernel and the issue disappeared.

I now have two VMs, with the same configuration, both yakkety, one with
kernel 4.8.0-26-generic and one with 4.4.0-45-generic, on the same
XenServer host. Here is what I see running host:

-------- 4.4.0-45 ----------------
$ time host www.google.com
www.google.com has address 216.58.198.4
www.google.com has IPv6 address 2a00:1450:4002:801::2004

real    0m0.051s
user    0m0.032s
sys     0m0.016s

-------- 4.8.0-26 ---------------
$ time host www.google.com
www.google.com has address 216.58.198.4
www.google.com has IPv6 address 2a00:1450:4002:801::2004

real    0m0.412s
user    0m0.296s
sys     0m0.096s


I have other yakkety hosts on VMware and even on another XenServer 7.0 with no 
noticeable issues, it just seems to happen on this cluster.

In the next days I will upgrade this cluster to XenServer 7.0 and I will
update the bug telling if the hypervisor version is a factor.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: linux-image-4.8.0-26-generic 4.8.0-26.28
ProcVersionSignature: Ubuntu 4.8.0-26.28-generic 4.8.0
Uname: Linux 4.8.0-26-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116,  1 Oct 27 20:02 seq
 crw-rw---- 1 root audio 116, 33 Oct 27 20:02 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.3-0ubuntu8
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:
Date: Sat Oct 29 00:37:00 2016
HibernationDevice: RESUME=UUID=4ab77eb2-d96a-42d5-be31-b4d499646269
InstallationDate: Installed on 2011-09-19 (1866 days ago)
InstallationMedia: Ubuntu-Server 11.10 "Oneiric Ocelot" - Beta amd64 (20110901)
IwConfig:
 lo        no wireless extensions.
 
 eth1      no wireless extensions.
 
 eth0      no wireless extensions.
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] 
failed with exit code 1: Hint: You are currently not seeing messages from other 
users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
Lsusb:
 Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd 
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: Xen HVM domU
PciMultimedia:
 
ProcFB: 0 cirrusdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.8.0-26-generic 
root=UUID=0c869ff8-8fe7-41b9-89f3-9da4882b4e87 ro init=/lib/systemd/systemd
RelatedPackageVersions:
 linux-restricted-modules-4.8.0-26-generic N/A
 linux-backports-modules-4.8.0-26-generic  N/A
 linux-firmware                            1.161
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: Upgraded to yakkety on 2016-10-14 (14 days ago)
WifiSyslog:
 
dmi.bios.date: 09/30/2016
dmi.bios.vendor: Xen
dmi.bios.version: 4.4.1-xs129783
dmi.chassis.type: 1
dmi.chassis.vendor: Xen
dmi.modalias: 
dmi:bvnXen:bvr4.4.1-xs129783:bd09/30/2016:svnXen:pnHVMdomU:pvr4.4.1-xs129783:cvnXen:ct1:cvr:
dmi.product.name: HVM domU
dmi.product.version: 4.4.1-xs129783
dmi.sys.vendor: Xen

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug yakkety

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1637666

Title:
  Heavy system slowdown with 4.8.0 kernel under XenServer

Status in linux package in Ubuntu:
  New

Bug description:
  Hello,

  I am experiencing a noticeable system slowdown since I upgraded from
  Xenial to Yakkety on several VM under XenServer 6.5 (fully patched).

  I understand it will be difficult for me to describe what is happening
  and for you to troubleshoot this issue but I'll try to do my best.

  Just after booting the machine is pretty responsive but after some
  time it starts responding very slowly.

  Bash autocompletion for file paths takes 1-2 seconds to respond,
  commands as "host" take hundred of milliseconds consuming hundred of
  ms of CPU. Compiling is an order of magnitude slower, etc.

  I wasn't able to detect what is causing the slowness. I tried to
  strace slow process with no evident cause. It does not seem to be
  something I/O bound.

  I ran "host" in an infinite loop causing 100% CPU usage seen from
  XenServer, 100% CPU usage in top but the sum of CPU usage from the
  processes is under 10%.

  top - 00:51:48 up 1 day,  4:49,  3 users,  load average: 1.47, 1.02, 0.59
  Tasks: 144 total,   2 running, 142 sleeping,   0 stopped,   0 zombie
  %Cpu(s): 74.4 us, 24.4 sy,  0.0 ni,  1.1 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 
st
  KiB Mem :  4044600 total,  1719740 free,   843100 used,  1481760 buff/cache
  KiB Swap:  2095100 total,  2095100 free,        0 used.  3139664 avail Mem 

    PID USER      PR  NI   VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND     
                                                     
  30968 yggdra    20   0  13460    696    616 R  5.8  0.0   0:00.18 host        
                                                     
  28790 root      20   0  42020   3748   3104 R  0.6  0.1   0:02.47 top   
  [...]

  
  I downgraded to the last Xenial kernel and the issue disappeared.

  I now have two VMs, with the same configuration, both yakkety, one
  with kernel 4.8.0-26-generic and one with 4.4.0-45-generic, on the
  same XenServer host. Here is what I see running host:

  -------- 4.4.0-45 ----------------
  $ time host www.google.com
  www.google.com has address 216.58.198.4
  www.google.com has IPv6 address 2a00:1450:4002:801::2004

  real    0m0.051s
  user    0m0.032s
  sys     0m0.016s

  -------- 4.8.0-26 ---------------
  $ time host www.google.com
  www.google.com has address 216.58.198.4
  www.google.com has IPv6 address 2a00:1450:4002:801::2004

  real    0m0.412s
  user    0m0.296s
  sys     0m0.096s

  
  I have other yakkety hosts on VMware and even on another XenServer 7.0 with 
no noticeable issues, it just seems to happen on this cluster.

  In the next days I will upgrade this cluster to XenServer 7.0 and I
  will update the bug telling if the hypervisor version is a factor.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.10
  Package: linux-image-4.8.0-26-generic 4.8.0-26.28
  ProcVersionSignature: Ubuntu 4.8.0-26.28-generic 4.8.0
  Uname: Linux 4.8.0-26-generic x86_64
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Oct 27 20:02 seq
   crw-rw---- 1 root audio 116, 33 Oct 27 20:02 timer
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
  ApportVersion: 2.20.3-0ubuntu8
  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:
  Date: Sat Oct 29 00:37:00 2016
  HibernationDevice: RESUME=UUID=4ab77eb2-d96a-42d5-be31-b4d499646269
  InstallationDate: Installed on 2011-09-19 (1866 days ago)
  InstallationMedia: Ubuntu-Server 11.10 "Oneiric Ocelot" - Beta amd64 
(20110901)
  IwConfig:
   lo        no wireless extensions.
   
   eth1      no wireless extensions.
   
   eth0      no wireless extensions.
  JournalErrors:
   Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] 
failed with exit code 1: Hint: You are currently not seeing messages from other 
users and the system.
         Users in the 'systemd-journal' group can see all messages. Pass -q to
         turn off this notice.
   No journal files were opened due to insufficient permissions.
  Lsusb:
   Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd 
   Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
  MachineType: Xen HVM domU
  PciMultimedia:
   
  ProcFB: 0 cirrusdrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.8.0-26-generic 
root=UUID=0c869ff8-8fe7-41b9-89f3-9da4882b4e87 ro init=/lib/systemd/systemd
  RelatedPackageVersions:
   linux-restricted-modules-4.8.0-26-generic N/A
   linux-backports-modules-4.8.0-26-generic  N/A
   linux-firmware                            1.161
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
  SourcePackage: linux
  UpgradeStatus: Upgraded to yakkety on 2016-10-14 (14 days ago)
  WifiSyslog:
   
  dmi.bios.date: 09/30/2016
  dmi.bios.vendor: Xen
  dmi.bios.version: 4.4.1-xs129783
  dmi.chassis.type: 1
  dmi.chassis.vendor: Xen
  dmi.modalias: 
dmi:bvnXen:bvr4.4.1-xs129783:bd09/30/2016:svnXen:pnHVMdomU:pvr4.4.1-xs129783:cvnXen:ct1:cvr:
  dmi.product.name: HVM domU
  dmi.product.version: 4.4.1-xs129783
  dmi.sys.vendor: Xen

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