Re: [Qemu-devel] [Qemu-block] Migration sometimes fails with IDE and Qemu 2.2.1

[Peter Lieven <pl@kamp.de>]

Am 09.04.2015 um 14:49 schrieb Peter Lieven:
> Am 07.04.2015 um 21:01 schrieb Dr. David Alan Gilbert:
>> * Peter Lieven (pl@kamp.de) wrote:
>>> Am 07.04.2015 um 17:29 schrieb Dr. David Alan Gilbert:
>>>> * Peter Lieven (pl@kamp.de) wrote:
>>>>> Hi David,
>>>>>
>>>>> Am 07.04.2015 um 10:43 schrieb Dr. David Alan Gilbert:
>>>>>>>>> Any particular workload or reproducer?
>>>>>>>> Workload is almost zero. I try to figure out if there is a way to trigger it.
>>>>>>>>
>>>>>>>> Maybe playing a role: Machine type is -M pc1.2 and we set -kvmclock as
>>>>>>>> CPU flag since kvmclock seemed to be quite buggy in 2.6.16...
>>>>>>>>
>>>>>>>> Exact cmdline is:
>>>>>>>> /usr/bin/qemu-2.2.1  -enable-kvm  -M pc-1.2 -nodefaults -netdev type=tap,id=guest2,script=no,downscript=no,ifname=tap2 -device e1000,netdev=guest2,mac=52:54:00:ff:00:65 -drive 
>>>>>>>> format=raw,file=iscsi://172.21.200.53/iqn.2001-05.com.equallogic:4-52aed6-88a7e99a4-d9e00040fdc509a3-XXX-hd0/0,if=ide,cache=writeback,aio=native -serial null  -parallel null  -m 1024 -smp 2,sockets=1,cores=2,threads=1  -monitor 
>>>>>>>> tcp:0:4003,server,nowait -vnc :3 -qmp tcp:0:3003,server,nowait -name 'XXX' -boot order=c,once=dc,menu=off  -drive index=2,media=cdrom,if=ide,cache=unsafe,aio=native,readonly=on -k de  -incoming tcp:0:5003  -pidfile /var/run/qemu/vm-146.pid  
>>>>>>>> -mem-path /hugepages -mem-prealloc  -rtc base=utc -usb -usbdevice tablet -no-hpet -vga cirrus  -cpu qemu64,-kvmclock
>>>>>>>>
>>>>>>>> Exact kernel is:
>>>>>>>> 2.6.16.46-0.12-smp (i think this is SLES10 or sth.)
>>>>>>>>
>>>>>>>> The machine does not hang. It seems just I/O is hanging. So you can type at the console or ping the system, but no longer login.
>>>>>>>>
>>>>>>>> Thank you,
>>>>>>>> Peter
>>>>>>> Interesting observation: Migrating the vServer again seems to fix to problem (at least in one case I could test just now).
>>>>>>>
>>>>>>> 2.6.8-24-smp is also affected.
>>>>>> How often does it fail - you say 'sometimes' - is it a 1/10 or a 1/1000 ?
>>>>> Its more often than 1/10 I would say.
>>>> OK, that's not too bad - it's the 1/1000 that are really nasty to find.
>>>> In your setup, how easy would it be for you to try :
>>>>      with either 2.1 or current head?
>>>>      with a newer machine-type?
>>>>      without the cdrom?
>>> Its all possible. I can clone the system and try everything on my test systems. I hope
>>> it reproduces there.
>> Great.  I think the order I would go would be:
>>      Try head - if it works we know we've already got the fix somewhere
>>      Try 2.1  - if it works we know it's something we introduced between
>>                 2.1 and 2.2.1
>>      Try a newer machine type - because pc-1.2 probably isn't tested much
>>      CDROM at the end.
>
> Update:
>  - head -> not working
>  - 2.1.3 -> not working
>  - without CROM -> not working
>  - with head and no machine type specified -> not working
>  - with -device isa-ide -> BIOS not booting harddisk
>
> Will now try 1.3.1 just to be sure.

1.3.1 => not working
kernel parameter ide=nodma (ide-core.nodma not supported by kernel) => not working.

I usually crash in my setup at around 50-80 migrations. In production it seems to happen more often.
Maybe it is load depending.

Peter