Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap()

[Christoph Hellwig]

On Wed, Mar 06, 2019 at 02:18:07AM -0500, Jason Wang wrote:
> 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. This is done through setup kernel address through vmap() and
> resigter MMU notifier for invalidation.
> 
> Test shows about 24% improvement on TX PPS. TCP_STREAM doesn't see
> obvious improvement.

How is this going to work for CPUs with virtually tagged caches?