[RFC PATCH V2 0/3] vhost: accelerate metadata access through vmap()

[Jason Wang]

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.

Changes from V1:
- instead of pinning pages, use MMU notifier to invalidate vmaps and
  remap duing metadata prefetch
- fix build warning on MIPS

Please review

Jason Wang (3):
  vhost: generalize adding used elem
  vhost: fine grain userspace memory accessors
  vhost: access vq metadata through kernel virtual address

 drivers/vhost/net.c   |   4 +-
 drivers/vhost/vhost.c | 362 ++++++++++++++++++++++++++++++++++++++----
 drivers/vhost/vhost.h |  15 +-
 3 files changed, 348 insertions(+), 33 deletions(-)

-- 
2.17.1