Re: [Qemu-devel] [PATCH 3/10] Add bdrv_flush_all()

Avi Kivity
2008-09-10T15:39:49Z

Anthony Liguori wrote:
>
> I'm actually liking bdrv_flush_all() less and less. If there are any
> outstanding IO requests, it will increase the down time associated
> with live migration. I think we definitely need to add a live save
> handler that waits until there are no outstanding IO requests to
> converge. I'm concerned though that it's not totally unreasonable to
> expect a guest to always have an IO request in flight.

I/O requests should complete in milliseconds; I don't see them as
increasing migration latency.

> That leads me to think that maybe we should be cancelling outstanding
> requests, and somehow saving their state?

Migration is enough of a special case that we should avoid special cases
within it as much as possible.

--
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