Il 19/03/2013 15:10, Michael R. Hines ha scritto:
On 03/19/2013 09:45 AM, Paolo Bonzini wrote:
This is because of downtime: You have to drain the queue anyway at the
very end, and if you don't drain it in advance after each iteration, then
the queue will have lots of bytes in it waiting for transmission and the
Virtual Machine will be stopped for a much longer period of time during
the last iteration waiting for RDMA card to finish transmission of all
those
bytes.
Shouldn't the "current chunk full" case take care of it too?
Of course if you disable chunking you have to add a different condition,
perhaps directly into save_rdma_page.
No, we don't want to flush on "chunk full" - that has a different meaning.
We want to have as many chunks submitted to the hardware for transmission
as possible to keep the bytes moving.
That however gives me an idea... Instead of the full drain at the end
of an iteration, does it make sense to do a "partial" drain at every
chunk full, so that you don't have > N bytes pending and the downtime is
correspondingly limited?