Re: [Qemu-devel] [PATCH 2/10] Allow the monitor to be suspended during non-blocking op

Avi Kivity
2008-09-11T10:19:08Z

Jamie Lokier wrote:
> Avi Kivity wrote:
>
>> (logically we would copy all of the data of all block devices, but
>> that's not very practical, so we assume shared storage).
>>
>
> Speaking of that, if the guest RAM were a memory-mapped file, couldn't
> that use shared storage too?
>
>

You would need a clustered filesystem that supports coherent mmap()s.

> You'd have to be careful: it would need a distributed filesystem with
> coherent mappings (i.e. not NFS), but they do exist.
>
> I'm guessing that the bulk of time spent in migration/checkpointing is
> saving the RAM image. Using a memory-mapped file on shared storage
> for RAM might make that faster. (Or slower!).
>

The memory needs to be transferred anyway, so total time would not
change. You could start running on the target sooner, though.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.