On Mon, Jun 2, 2014 at 8:43 PM, Zhang Haoyu <zhanghy@xxxxxxxxxxx> wrote: >>A few additional questions:) >> >>1. If IO to a block device goes through QEMU and not vhost, are there >>data copies between kernel and user mode if I do IO to a block device >>or is it zero copy? Kind of related to Question (2) also. >> > I'm not sure, it perhaps depend on which IO mode you chose, qemu pthreads IO, or linux AIO? > Somebody else do a favour, please. That would be definitely good to know:) I didnt know about the modes as such. Can you clarify? Are you talking about vhost-LIO vs Qemu? The LIO part, I do believe, is zero copy.. I have seen pretty high memory usage on QEMU thread, not sure why. > >>2. A related question to (1), is the QEMU process separate from the VM >>process or do they all run on the same process as different threads? I >>did read about IO threads and it seemed like they are all part of the >>same process, wanted to confirm. >> > Yes, vcpu threads and qemu backend IO threads belong to the same process(qemu). > >>Thank you:) > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
