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Message #21979
[Bug 1717224] Re: virsh start of virtual guest domain fails with internal error due to low default aio-max-nr sysctl value
Commit 2a8a98673c13 has been in Xenial and Artful for some time now.
Can you confirm this bug is now resolved with the latest updates.
** Changed in: linux (Ubuntu Artful)
Status: In Progress => Fix Released
** Changed in: linux (Ubuntu Xenial)
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1717224
Title:
virsh start of virtual guest domain fails with internal error due to
low default aio-max-nr sysctl value
Status in Ubuntu on IBM z Systems:
In Progress
Status in kvm package in Ubuntu:
Won't Fix
Status in linux package in Ubuntu:
Fix Released
Status in procps package in Ubuntu:
New
Status in linux source package in Xenial:
Fix Released
Status in procps source package in Xenial:
New
Status in linux source package in Artful:
Fix Released
Status in procps source package in Artful:
New
Bug description:
Starting virtual guests via on Ubuntu 16.04.2 LTS installed with its
KVM hypervisor on an IBM Z14 system LPAR fails on the 18th guest with
the following error:
root@zm93k8:/rawimages/ubu1604qcow2# virsh start zs93kag70038
error: Failed to start domain zs93kag70038
error: internal error: process exited while connecting to monitor: 2017-07-26T01:48:26.352534Z qemu-kvm: -drive file=/guestimages/data1/zs93kag70038.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none,aio=native: Could not open backing file: Could not set AIO state: Inappropriate ioctl for device
The previous 17 guests started fine:
root@zm93k8# virsh start zs93kag70020
Domain zs93kag70020 started
root@zm93k8# virsh start zs93kag70021
Domain zs93kag70021 started
.
.
root@zm93k8:/rawimages/ubu1604qcow2# virsh start zs93kag70036
Domain zs93kag70036 started
We ended up fixing the issue by adding the following line to /etc/sysctl.conf :
fs.aio-max-nr = 4194304
... then, reload the sysctl config file:
root@zm93k8:/etc# sysctl -p /etc/sysctl.conf
fs.aio-max-nr = 4194304
Now, we're able to start more guests...
root@zm93k8:/etc# virsh start zs93kag70036
Domain zs93kag70036 started
The default value was originally set to 65535:
root@zm93k8:/rawimages/ubu1604qcow2# cat /proc/sys/fs/aio-max-nr
65536
Note, we chose the 4194304 value, because this is what our KVM on System Z hypervisor ships as its default value. Eg. on our zKVM system:
[root@zs93ka ~]# cat /proc/sys/fs/aio-max-nr
4194304
ubuntu@zm93k8:/etc$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.2 LTS
Release: 16.04
Codename: xenial
ubuntu@zm93k8:/etc$
ubuntu@zm93k8:/etc$ dpkg -s qemu-kvm |grep Version
Version: 1:2.5+dfsg-5ubuntu10.8
Is something already documented for Ubuntu KVM users warning them about the low default value, and some guidance as to
how to select an appropriate value? Also, would you consider increasing the default aio-max-nr value to something much
higher, to accommodate significantly more virtual guests?
Thanks!
---uname output---
ubuntu@zm93k8:/etc$ uname -a Linux zm93k8 4.4.0-62-generic #83-Ubuntu SMP Wed Jan 18 14:12:54 UTC 2017 s390x s390x s390x GNU/Linux
Machine Type = z14
---Debugger---
A debugger is not configured
---Steps to Reproduce---
See Problem Description.
The problem was happening a week ago, so this may not reflect that
activity.
This file was collected on Aug 7, one week after we were hitting the
problem. If I need to reproduce the problem and get fresh data,
please let me know.
/var/log/messages doesn't exist on this system, so I provided syslog
output instead.
All data have been collected too late after the problem was observed
over a week ago. If you need me to reproduce the problem and get new
data, please let me know. That's not a problem.
Also, we would have to make special arrangements for login access to
these systems. I'm happy to run traces and data collection for you as
needed. If that's not sufficient, then we'll explore log in access
for you.
Thanks... - Scott G.
I was able to successfully recreate the problem and captured / attached new debug docs.
Recreate procedure:
# Started out with no virtual guests running.
ubuntu@zm93k8:/home/scottg$ virsh list
Id Name State
----------------------------------------------------
# Set fs.aio-max-nr back to original Ubuntu "out of the box" value in /etc/sysctl.conf
ubuntu@zm93k8:~$ tail -1 /etc/sysctl.conf
fs.aio-max-nr = 65536
## sysctl -a shows:
fs.aio-max-nr = 4194304
## Reload sysctl.
ubuntu@zm93k8:~$ sudo sysctl -p /etc/sysctl.conf
fs.aio-max-nr = 65536
ubuntu@zm93k8:~$
ubuntu@zm93k8:~$ sudo sysctl -a |grep fs.aio-max-nr
fs.aio-max-nr = 65536
ubuntu@zm93k8:~$ cat /proc/sys/fs/aio-max-nr
65536
# Attempt to start more than 17 qcow2 virtual guests on the Ubuntu
host. Fails on the 18th XML.
Script used to start guests..
ubuntu@zm93k8:/home/scottg$ date;./start_privs.sh
Wed Aug 23 13:21:25 EDT 2017
virsh start zs93kag70015
Domain zs93kag70015 started
Started zs93kag70015 succesfully ...
virsh start zs93kag70020
Domain zs93kag70020 started
Started zs93kag70020 succesfully ...
virsh start zs93kag70021
Domain zs93kag70021 started
Started zs93kag70021 succesfully ...
virsh start zs93kag70022
Domain zs93kag70022 started
Started zs93kag70022 succesfully ...
virsh start zs93kag70023
Domain zs93kag70023 started
Started zs93kag70023 succesfully ...
virsh start zs93kag70024
Domain zs93kag70024 started
Started zs93kag70024 succesfully ...
virsh start zs93kag70025
Domain zs93kag70025 started
Started zs93kag70025 succesfully ...
virsh start zs93kag70026
Domain zs93kag70026 started
Started zs93kag70026 succesfully ...
virsh start zs93kag70027
Domain zs93kag70027 started
Started zs93kag70027 succesfully ...
virsh start zs93kag70028
Domain zs93kag70028 started
Started zs93kag70028 succesfully ...
virsh start zs93kag70029
Domain zs93kag70029 started
Started zs93kag70029 succesfully ...
virsh start zs93kag70030
Domain zs93kag70030 started
Started zs93kag70030 succesfully ...
virsh start zs93kag70031
Domain zs93kag70031 started
Started zs93kag70031 succesfully ...
virsh start zs93kag70032
Domain zs93kag70032 started
Started zs93kag70032 succesfully ...
virsh start zs93kag70033
Domain zs93kag70033 started
Started zs93kag70033 succesfully ...
virsh start zs93kag70034
Domain zs93kag70034 started
Started zs93kag70034 succesfully ...
virsh start zs93kag70035
Domain zs93kag70035 started
Started zs93kag70035 succesfully ...
virsh start zs93kag70036
error: Failed to start domain zs93kag70036
error: internal error: process exited while connecting to monitor: 2017-08-23T17:21:47.131809Z qemu-kvm: -drive file=/guestimages/data1/zs93kag70036.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none,aio=native: Could not open backing file: Could not set AIO state: Inappropriate ioctl for device
Exiting script ... start zs93kag70036 failed
ubuntu@zm93k8:/home/scottg$
# Show that there are only 17 running guests.
ubuntu@zm93k8:/home/scottg$ virsh list |grep run |wc -l
17
ubuntu@zm93k8:/home/scottg$ virsh list
Id Name State
----------------------------------------------------
25 zs93kag70015 running
26 zs93kag70020 running
27 zs93kag70021 running
28 zs93kag70022 running
29 zs93kag70023 running
30 zs93kag70024 running
31 zs93kag70025 running
32 zs93kag70026 running
33 zs93kag70027 running
34 zs93kag70028 running
35 zs93kag70029 running
36 zs93kag70030 running
37 zs93kag70031 running
38 zs93kag70032 running
39 zs93kag70033 running
40 zs93kag70034 running
41 zs93kag70035 running
# For fun, try starting zs93kag70036 again manually.
ubuntu@zm93k8:/home/scottg$ date;virsh start zs93kag70036
Wed Aug 23 13:27:28 EDT 2017
error: Failed to start domain zs93kag70036
error: internal error: process exited while connecting to monitor: 2017-08-23T17:27:30.031782Z qemu-kvm: -drive file=/guestimages/data1/zs93kag70036.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none,aio=native: Could not open backing file: Could not set AIO state: Inappropriate ioctl for device
# Show the XML (they're all basically the same)...
ubuntu@zm93k8:/home/scottg$ cat zs93kag70036.xml
<domain type='kvm'>
<name>zs93kag70036</name>
<memory unit='MiB'>4096</memory>
<currentMemory unit='MiB'>2048</currentMemory>
<vcpu placement='static'>2</vcpu>
<os>
<type arch='s390x' machine='s390-ccw-virtio'>hvm</type>
</os>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>preserve</on_crash>
<devices>
<emulator>/usr/bin/qemu-kvm</emulator>
<disk type='file' device='disk'>
<driver name ='qemu' type='qcow2' cache='none' io='native'/>
<source file='/guestimages/data1/zs93kag70036.qcow2'/>
<target dev='vda' bus='virtio'/>
<address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0000'/>
<boot order='1'/>
</disk>
<interface type='network'>
<source network='privnet1'/>
<model type='virtio'/>
<mac address='52:54:00:70:d0:36'/>
<address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0001'/>
</interface>
<!--
<disk type='block' device='disk'>
<driver name ='qemu' type='raw' cache='none'/>
<source dev='/dev/disk/by-id/dm-uuid-mpath-36005076802810e5540000000000006e4'/>
<target dev='vde' bus='virtio'/>
<address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0005'/>
<readonly/>
</disk>
-->
<disk type='file' device='disk'>
<driver name ='qemu' type='raw' cache='none' io='native'/>
<source file='/guestimages/data1/zs93kag70036.prm'/>
<target dev='vdf' bus='virtio'/>
<address type='ccw' cssid='0xfe' ssid='0x0' devno='0x0006'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source file='/guestimages/data1/zs93kag70036.iso'/>
<target dev='sda' bus='scsi'/>
<readonly/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
<controller type='usb' index='0' model='none'/>
<memballoon model='none'/>
<console type='pty'>
<target type='sclp' port='0'/>
</console>
</devices>
</domain>
This condition is very easy to replicate. However, we may be losing this system in the next day or two, so please let me know ASAP if you need any more data. Thank you...
- Scott G.
== Comment: #11 - Viktor Mihajlovski <MIHAJLOV@xxxxxxxxxx> - 2017-09-14
In order to support many KVM guests it is advisable to raise the aio-max-nr as suggested in the problem description, see also http://kvmonz.blogspot.co.uk/p/blog-page_7.html. I would also suggest that the system default setting is increased.
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