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

[Gerhard Wiesinger <gerhard@wiesinger.com>]

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

Ciao,
Gerhard