Hi Pavel,

I tested as advised. And aaaaaaargh hit the next two OVirt bugs....

https://bugzilla.redhat.com/show_bug.cgi?id=1326900

Nevertheless: Merging only one disk at once works as expected.
The VM stays up, keeps running and is responsive.

Markus
________________________________________
Von: Pavel Gashev [p...@acronis.com]
Gesendet: Mittwoch, 13. April 2016 15:12
An: Markus Stockhausen; users
Betreff: Re: AW: [ovirt-users] stalls during live Merge Centos 7 / qemu 2.3

Markus,

So all CPU threads are blocked by the main loop. The main loop is busy draining 
IO requests from all drives while there are other block commit jobs active... 
It looks like currently QEMU just can't live merge more than one drive 
simultaneously without blocking VCPUs.

As workaround you can delete disk snapshots one-by-one, and then delete 
disk-less VM snapshot. The Storage tab has Disk Snapshots sub tab where you can 
remove a specific snapshot of a specific disk.





On 12/04/16 21:39, "Markus Stockhausen" <stockhau...@collogia.de> wrote:

>> Von: Pavel Gashev [p...@acronis.com]
>> Gesendet: Dienstag, 12. April 2016 16:15
>> An: Markus Stockhausen; users
>> Betreff: Re: [ovirt-users] stalls during live Merge Centos 7 / qemu 2.3
>>
>> Markus,
>>
>> I saw similar issues. Looks like it's related to multidisk VMs under high 
>> disk load. No relations with guest OS. No relations with IO threads.
>>
>>
>> I didn't debug it. Can you please show a backtrace of a thread in 
>> __lll_lock_wait ?
>
>Hi Pavel.
>
>thanks for your response. I dont even need high disk load to
>reproduce the issue. Just a simple script that writes 8k blocks
>every 0.5 secs.  I added the required info to the BZ.
>
>https://bugzilla.redhat.com/show_bug.cgi?id=1319400
>
>Markus
>
>>
>>
>> On 11/04/16 18:13, "users-boun...@ovirt.org on behalf of Markus Stockhausen" 
>> <users-boun...@ovirt.org on behalf of stockhau...@collogia.de> wrote:
>>
>> >Hi there,
>> >
>> >I'm getting slowly mad about our new Centos 7 cluster. Whenever
>> >I start a live merge the machine completely freezes. It seems to be
>> >independent of the Guest OS (tried SLES 11 SP3, SLES11 SP4 and
>> >SLES12). I already opened BZ1319400 because I'm clueless.
>> >
>> >Doing the same in our Fedora 20 cluster (qemu 2.1.3) we only see
>> >small hiccups of 1-3 seconds at the start of the live merge but no
>> >complete stall. Its the same VM!
>> >
>> >Just to be sure that it is not a specific problem of our topology
>> >or SLES I would like to receive some feedback of the list if anyone
>> >observes similar lockups in their environment.
>> >
>> >Thanks in advance.
>> >
>> >Markus
>> >
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