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Re: [Qemu-devel] Migration downtime more than 5s when migrating guest wi
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] Migration downtime more than 5s when migrating guest with massive disks |
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Date: |
Mon, 22 May 2017 14:26:10 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 20/05/2017 02:46, Yang Hongyang wrote:
>>> How about do O(1) for stopping stage of live migration?
>>> Because the cpu is stopped in this phase, it wouldn't cause
>>> side effects IMHO, right?
>> O(1) update is probably not quite possible, but it's possible to do one
>> O(n) update. We tried doing that, but something in virtio broke.
> How were you do that? did you put extra begin/commit before/after destination
> guest load, so that the destination guest only do one update(of n devs)
> throughout
> the whole migration?
>
Right. However, this is a problem if post_load hooks do DMA. You need
to move that DMA to a VM RunState change notifier.
Paolo