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Re: [Qemu-devel] Overcommiting cpu results in all vms offline
From: |
Stefan Priebe - Profihost AG |
Subject: |
Re: [Qemu-devel] Overcommiting cpu results in all vms offline |
Date: |
Mon, 17 Sep 2018 09:00:57 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
Hi,
Am 17.09.2018 um 08:38 schrieb Jack Wang:
> Stefan Priebe - Profihost AG <address@hidden> 于2018年9月16日周日 下午3:31写道:
>>
>> Hello,
>>
>> while overcommiting cpu I had several situations where all vms gone offline
>> while two vms saturated all cores.
>>
>> I believed all vms would stay online but would just not be able to use all
>> their cores?
>>
>> My original idea was to automate live migration on high host load to move
>> vms to another node but that makes only sense if all vms stay online.
>>
>> Is this expected? Anything special needed to archive this?
>>
>> Greets,
>> Stefan
>>
> Hi, Stefan,
>
> Do you have any logs when all VMs go offline?
> Maybe OOMkiller play a role there?
After reviewing i think this is memory related but OOM did not play a role.
All kvm processes where spinning trying to get > 100% CPU and i was not
able to even login to ssh. After 5-10 minutes i was able to login.
There were about 150GB free mem.
Relevant settings (no local storage involved):
vm.dirty_background_ratio:
3
vm.dirty_ratio:
10
vm.min_free_kbytes:
10567004
# cat /sys/kernel/mm/transparent_hugepage/defrag
always defer [defer+madvise] madvise never
# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never
After that i had the following traces on the host node:
https://pastebin.com/raw/0VhyQmAv
Thanks!
Greets,
Stefan