Re: [Qemu-devel] Fedora FC21 - Bug: 100% CPU and hangs in gettimeofday(&tp, NULL); forever

[Gerhard Wiesinger <gerhard@wiesinger.com>]

On 02.03.2015 18:15, Gerhard Wiesinger wrote:
> On 02.03.2015 16:52, Gerhard Wiesinger wrote:
>> On 02.03.2015 10:26, Paolo Bonzini wrote:
>>>
>>> On 01/03/2015 11:36, Gerhard Wiesinger wrote:
>>>> So far it happened only the PostgreSQL database VM. Kernel is alive
>>>> (ping works well). ssh is not working.
>>>> console window: after entering one character at login prompt, then 
>>>> crashed:
>>>> [1438.384864] Out of memory: Kill process 10115 (pg_dump) score 112 or
>>>> sacrifice child
>>>> [1438.384990] Killed process 10115 (pg_dump) total-vm: 340548kB,
>>>> anon-rss: 162712kB, file-rss: 220kB
>>> Can you get a vmcore or at least sysrq-t output?
>>
>> Yes, next time it happens I can analyze it.
>>
>> I think there are 2 problems:
>> 1.) OOM (Out of Memory) problem with the low memory settings and 
>> kernel settings (see below)
>> 2.) Instability problem which might have a dependency to 1.)
>>
>> What I've done so far (thanks to Andrey Korolyov for ideas and help):
>> a.) Updated maschine type from pc-0.15 to pc-i440fx-2.2
>> virsh dumpxml database | grep "<type"
>>     <type arch='x86_64' machine='pc-0.15'>hvm</type>
>>
>> virsh edit database
>> virsh dumpxml database | grep "<type"
>>     <type arch='x86_64' machine='pc-i440fx-2.2'>hvm</type>
>>
>> SMBIOS is updated therefore from 2.4 to 2.8:
>> dmesg|grep -i SMBIOS
>> [    0.000000] SMBIOS 2.8 present.
>> b.) Switched to tsc clock, kernel parameters: clocksource=tsc 
>> nohz=off highres=off
>> c.) Changed overcommit to 1
>> echo "vm.overcommit_memory = 1" > /etc/sysctl.d/overcommit.conf
>> d.) Tried 1 VCPU instead of 2
>> e.) Installed 512MB vRAM instead of 384MB
>> f.) Prepared for sysrq and vmcore
>> echo "kernel.sysrq = 1" > /etc/sysctl.d/sysrq.conf
>> sysctl -w kernel.sysrq=1
>> virsh send-key database KEY_LEFTALT KEY_SYSRQ KEY_T
>> virsh dump domain-name /tmp/dumpfile
>> g.) Further ideas, not yet done: disable memory balooning by 
>> blacklisting baloon driver or remove from virsh xml config
>>
>> Summary:
>> 1.) 512MB, tsc timer, 1VCPU, vm.overcommit_memory = 1: no OOM 
>> problem, no crash
>> 2.) 512MB, kvm_clock, 2VCPU, vm.overcommit_memory = 1: no OOM 
>> problem, no crash
>
> 3.) 384MB, kvm_clock, 2VCPU, vm.overcommit_memory = 1: no OOM problem, 
> no crash

3b.) Still happened again at the nightly backup with same configuration 
as in 3.) configuration 384MB, kvm_clock, 2VCPU, vm.overcommit_memory = 
1, pc-i440fx-2.2: no OOM problem, ping ok, no reaction, BUT CRASHED again

SYSRQ: no reaction of the VM
virsh send-key vm KEY_LEFTALT KEY_SYSRQ KEY_T

virsh dump vm file.core
error: Failed to core dump domain vm to file.core
error: internal error: unable to execute QEMU command 'migrate': State 
blocked by non-migratable device '0000:00:09.0/ich9_ahci'

Removed the SATA controller, dump should work for the future.

Any futher ideas?

Ciao,
Gerhard