Re: [libvirt] MemoryPeek() is slow
On Tue, Jul 21, 2009 at 7:50 PM, Daniel P. Berrange<berrange(a)redhat.com> wrote:
On Tue, Jul 21, 2009 at 07:39:07PM +0900, Jun Koi wrote:
> Hi,
>
> I play around with MemoryPeek() API on QEMU. While it works well, I
> found that it is too slow.
Slow in what context ? Are you trying to read large amounts of
data out of the guest ?
Yes.
> That is expected because of the way it works: we always need to save
> memory to a file, and read it in again, and that is too inefficient.
Possibly, but there's quite a few other variables in the stack that
could impact performance too. eg you've got at least 3 more data
copies in the libvirt RPC layer ontop of that. Also the libvirt RPC
layer and API for memory peek has synchronous round-trips which will
result in bad throughput if making lot sof peek calls in a row
> I am trying to figure out a better way to do this. To do that, clearly
> we need to re-architecture QEMU for this: We must have another way to
> read memory from outside the QEMU process.
>
> Anybody could suggest a solution for this problem? I am willing to
> spend time on this feature to improve the situation.
Could you explain in more detail what you are using the memory peek
API for ? That might suggest a completely different libvirt API, or
even something outside of libvirft
That is nothing special. I am working on something like virt-top,
which requires to read VM's memory.
I am also doing some experiments, which requires to get data out as
fast as possible.
Really I dont think that current multiple layers are the culprit of
the slow problem. It must be the way we are reading memory out, as I
wrote above. That is way to inefficient, and nobody can deny that.
Thanks,
J