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Re: [Qemu-devel] migrate_set_speed has no effect if the guest is using h
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From: |
Dr. David Alan Gilbert |
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Subject: |
Re: [Qemu-devel] migrate_set_speed has no effect if the guest is using hugepages. |
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Date: |
Thu, 11 Jul 2019 11:24:10 +0100 |
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User-agent: |
Mutt/1.12.0 (2019-05-25) |
* Lin Ma (address@hidden) wrote:
> Hi all,
Hi Lin,
> When I live migrate a qemu/kvm guest, If the guest is using huge pages, I
> found that
> the migrate_set_speed command had no effect during stage 2.
Can you explain what you mean by 'stage 2'?
> It was caused by commit 4c011c3 postcopy: Send whole huge pages
>
> I'm wondering that is it by design or is it a bug waiting for fix?
This is the first report I've seen for it. How did you conclude that
4c011c3 caused it? While I can see it might have some effect on the
bandwidth management, I'm surprised it has this much effect.
What size huge pages are you using - 2MB or 1GB?
I can imagine we might have a problem that since we only do the sleep
between the hugepages, if we were using 1GB hugepages then
we'd see <big chunk of data>[sleep]<big chunk of data>[sleep]
which isn't as smooth as it used to be.
Can you give me some more details of your test?
Dave
>
> Thanks,
> Lin
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK