Re: [Qemu-devel] setting migrate_downtime results in halted vm (qemu 1.3)

[Alexandre DERUMIER]

Hi list,
After discuss with Stefan Yesterday here some more info:

(this is for stable qemu 1.3, it was working fine with qemu 1.2)

The problem seem that whesettings a migrate_set_downtime to 1sec,

the transfert of the vm seem to send all the memory of the vm in 1 step, and 
not by increment.
So the downtime is really huge , 90000ms for 1GB memory.
And I think the monitor doesn't response during this last step transfert


with migrate_set_downtime 30ms, the memory is correctly sent by increment, then 
the last step result around 500ms of downtime.

I can't reproduce it myself, only difference seem to be 10GBE Network of 
stefan. ( migrate_set_speed is set to 8589934592)

Stefan can reproduce it 100%.

I think something must be wrong in arch_init.c, But I'm not expert with qemu 
migration code.
So If you have any ideas/clues....

Regards,

Alexandre



migrate_set_dowtime:1
----------------------
Dec 27 12:57:11 starting migration of VM 105 to node 'cloud1-1202'
(10.255.0.20)
Dec 27 12:57:11 copying disk images
Dec 27 12:57:11 starting VM 105 on remote node 'cloud1-1202'
Dec 27 12:57:15 starting migration tunnel
Dec 27 12:57:15 starting online/live migration on port 60000
Dec 27 12:57:15 migrate_set_speed: 8589934592
Dec 27 12:57:15 migrate_set_downtime: 1
-> query-migrate: monitor hang
-> query-migrate: monitor hang
-> query-migrate: monitor hang
-> query-migrate: (finished)Dec 27 12:58:45 migration speed: 22.76 MB/s - 
downtime 90004 ms
Dec 27 12:58:45 migration status: completed
Dec 27 12:58:49 migration finished successfuly (duration 00:01:38)
TASK OK


migrate_set_downtime:03

The same again with 1GB Memory and migrate_downtime set to 0.03 (cached
mem):
Dec 27 13:00:19 starting migration of VM 105 to node 'cloud1-1203'
(10.255.0.22)
Dec 27 13:00:19 copying disk images
Dec 27 13:00:19 starting VM 105 on remote node 'cloud1-1203'
Dec 27 13:00:22 starting migration tunnel
Dec 27 13:00:23 starting online/live migration on port 60000
Dec 27 13:00:23 migrate_set_speed: 8589934592
Dec 27 13:00:23 migrate_set_downtime: 0.03
-> query-migrate : Dec 27 13:00:25 migration status: active (transferred 
404647386, remaining 680390656), total 2156265472) , expected downtime 190
-> query-migrate : Dec 27 13:00:27 migration status: active (transferred 
880582320, remaining 203579392), total 2156265472) , expected downtime 53
-> query-migrate : (status finished);Dec 27 13:00:29 migration speed: 341.33 
MB/s - downtime 490 ms
Dec 27 13:00:29 migration status: completed
Dec 27 13:00:32 migration finished successfuly (duration 00:00:13)
TASK OK


----- Mail original -----

De: "Stefan Priebe" <address@hidden>
À: "qemu-devel" <address@hidden>
Envoyé: Jeudi 27 Décembre 2012 22:54:55
Objet: [Qemu-devel] setting migrate_downtime results in halted vm

Hello list,

i'm using qemu 1.3 and migration works fine if i do not set
migrate_downtime.

If i set migrate_downtime to 1s or 0.5s or 0.3s the VM halts immediatly
i cannot even connect to the qmp socket anymore and migration takes 5-10
minutes or never finishes.

I see high cpu usage on source vm while it hangs.

VM was for all tests IDLE and was using 1GB of 4GB mem.

Do you have any ideas what happens here?

Greets,
Stefan