** Changed in: linux (Ubuntu)
Assignee: (unassigned) => Chris J Arges (arges)
** Changed in: linux (Ubuntu)
Importance: Undecided => High
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https://bugs.launchpad.net/bugs/1413540
Title:
qemu-kvm package enables KSM on VMs
Status in linux package in Ubuntu:
Incomplete
Status in qemu package in Ubuntu:
Confirmed
Bug description:
When installing qemu-kvm on a VM, KSM is enabled.
I have encountered this problem in trusty:$ lsb_release -a
Distributor ID: Ubuntu
Description: Ubuntu 14.04.1 LTS
Release: 14.04
Codename: trusty
$ uname -a
Linux juju-gema-machine-2 3.13.0-40-generic #69-Ubuntu SMP Thu Nov 13
17:53:56 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
The way to see the behaviour:
1) $ more /sys/kernel/mm/ksm/run
0
2) $ sudo apt-get install qemu-kvm
3) $ more /sys/kernel/mm/ksm/run
1
To see the soft lockups, deploy a cloud on a virtualised env like ctsstack,
run tempest on it, the compute nodes of the virtualised deployment will
eventually stop responding with (run tempest 2 times at least):
24096.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
[24124.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791]
[24152.072002] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24180.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24208.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24236.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
[24264.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791]
I am not sure whether the problem is that we are enabling KSM on a VM
or the problem is that nested KSM is not behaving properly. Either way
I can easily reproduce, please contact me if you need further details.
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