[Qemu-devel] Re: [PATCH 09/10] Exit loop if we have been there too long

[Avi Kivity]

On 12/01/2010 03:52 AM, Juan Quintela wrote:
> >   - 512GB guest is really the target?
>
> no, problems exist with smaller amounts of RAM.  with 16GB guest it is
> trivial to get 1s stalls, 64GB guest, 3-4s, with more memory, migration
> is flaky to say the less.
>
> >   - how much cpu time can we use for these things?
>
> the problem here is that we are forced to walk the bitmap too many
> times, we want to do it less times.

How much time is spent walking bitmaps?  Are you sure this is the problem?

> >   - how many dirty pages do we have to care?
>
> default values and assuming 1Gigabit ethernet for ourselves ~9.5MB of
> dirty pages to have only 30ms of downtime.

1Gb/s * 30ms = 100 MB/s * 30 ms = 3 MB.


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