From: Jason Wang <jasowang@redhat.com>
Date: Fri, 14 Dec 2018 12:29:54 +0800

On 2018/12/14 上午4:12, Michael S. Tsirkin wrote:

quoted

On Thu, Dec 13, 2018 at 06:10:19PM +0800, Jason Wang wrote:

quoted

Hi:

This series tries to access virtqueue metadata through kernel virtual
address instead of copy_user() friends since they had too much
overheads like checks, spec barriers or even hardware feature
toggling.

Test shows about 24% improvement on TX PPS. It should benefit other
cases as well.

Please review

I think the idea of speeding up userspace access is a good one.
However I think that moving all checks to start is way too aggressive.

So did packet and AF_XDP. Anyway, sharing address space and access
them directly is the fastest way. Performance is the major
consideration for people to choose backend. Compare to userspace
implementation, vhost does not have security advantages at any
level. If vhost is still slow, people will start to develop backends
based on e.g AF_XDP.

Exactly, this is precisely how this kind of problem should be solved.

Michael, I strongly support the approach Jason is taking here, and I
would like to ask you to seriously reconsider your objections.

Thank you.