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From: | Marcin Gibuła |
Subject: | Re: [Qemu-devel] latest rc: virtio-blk hangs forever after migration |
Date: | Thu, 17 Jul 2014 13:20:26 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
I've reproduced your IO hang with 2.0 and both 9b1786829aefb83f37a8f3135e3ea91c56001b56 and a096b3a6732f846ec57dc28b47ee9435aa0609bf applied. Reverting 9b1786829aefb83f37a8f3135e3ea91c56001b56 indeed fixes the problem (but reintroduces block-migration hang). It's seems like qemu bug rather than guest problem, as no-kvmclock parameters makes no difference. IO just stops, all qemu IO threads die off. Almost like it forgets to migrate them:-)
Some more info:a) 2.0 + 9b1786829aefb83f37a8f3135e3ea91c56001b56 + a096b3a6732f846ec57dc28b47ee9435aa0609bf = hangs
b) 2.0 + 9b1786829aefb83f37a8f3135e3ea91c56001b56 = worksc) 2.0 + 9b1786829aefb83f37a8f3135e3ea91c56001b56 + move cpu_synchronize_state to migration.c = works
Tested with NFS (qcow2) + cache=none. IO is dead only for disk that was being written to during migration.I.e. if my test VM has two disks: vda and vdb, and I'm running fio on vdb and it hangs after migration, I can still issue writes to vda.
Recreation steps: 1. Create VM 2. Run fio (Andrey's config) 3. Live migrate VM couple of times. -- mg
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