Hello I had some basic questions, was asking them on the kvm list but it probably makes more sense here:) The questions are about virtio-scsi. I would appreciate any help. 1. Is virtio-scsi via QEMU a zero copy operation from guest to disk? The vhost-LIO as I understand it is zero copy, wasnt sure about QEMU. With the VM and the QEMU thread part of the same process, it would be good to know the flow and where the copies occur, if they do. 2. When the block layer underneath QEMU(assuming the QEMU does talk to the block device and not sg, for example), if an error code comes in, is it converted to a SCSI response before being passed to the guest? 3. Are there any other performance tweaks that would help in both the QEMU case and the LIO case? Thanks in advance:) MW
Hello, Just a bump:) I am hoping this is the right list to ask the question... MW. On Fri, Jun 6, 2014 at 7:15 PM, Marcus White <roastedseaweed.k@gmail.com> wrote:
Hello I had some basic questions, was asking them on the kvm list but it probably makes more sense here:)
The questions are about virtio-scsi. I would appreciate any help.
1. Is virtio-scsi via QEMU a zero copy operation from guest to disk? The vhost-LIO as I understand it is zero copy, wasnt sure about QEMU. With the VM and the QEMU thread part of the same process, it would be good to know the flow and where the copies occur, if they do.
2. When the block layer underneath QEMU(assuming the QEMU does talk to the block device and not sg, for example), if an error code comes in, is it converted to a SCSI response before being passed to the guest?
3. Are there any other performance tweaks that would help in both the QEMU case and the LIO case?
Thanks in advance:) MW
----- Original Message -----
From: "Marcus White" <roastedseaweed.k@gmail.com> To: devel@ovirt.org Sent: Thursday, June 12, 2014 9:49:14 PM Subject: Re: [ovirt-devel] virtio-scsi
Hello, Just a bump:) I am hoping this is the right list to ask the question...
MW.
I don't think so. The oVirt project is build on top of libvirt and qemu. qeum developers should be able to answer these questions. I would try here: http://wiki.qemu.org/MailingLists
On Fri, Jun 6, 2014 at 7:15 PM, Marcus White <roastedseaweed.k@gmail.com> wrote:
Hello I had some basic questions, was asking them on the kvm list but it probably makes more sense here:)
The questions are about virtio-scsi. I would appreciate any help.
1. Is virtio-scsi via QEMU a zero copy operation from guest to disk? The vhost-LIO as I understand it is zero copy, wasnt sure about QEMU. With the VM and the QEMU thread part of the same process, it would be good to know the flow and where the copies occur, if they do.
2. When the block layer underneath QEMU(assuming the QEMU does talk to the block device and not sg, for example), if an error code comes in, is it converted to a SCSI response before being passed to the guest?
3. Are there any other performance tweaks that would help in both the QEMU case and the LIO case?
Thanks in advance:) MW
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