On Fri, May 24, 2019 at 04:12:12AM -0400, Jason Wang wrote:

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 like SMAP. This is done through setup kernel address through
direct mapping and co-opreate VM management with MMU notifiers.

Test shows about 23% improvement on TX PPS. TCP_STREAM doesn't see
obvious improvement.

Thanks

Thanks this is queued for next.

Did you want to rebase and repost packed ring support on top?
IIUC it's on par with split ring with these patches.

Changes from RFC V3:
- rebase to net-next
- Tweak on the comments
Changes from RFC V2:
- switch to use direct mapping instead of vmap()
- switch to use spinlock + RCU to synchronize MMU notifier and vhost
  data/control path
- set dirty pages in the invalidation callbacks
- always use copy_to/from_users() friends for the archs that may need
  flush_dcache_pages()
- various minor fixes
Changes from V4:
- use invalidate_range() instead of invalidate_range_start()
- track dirty pages
Changes from V3:
- don't try to use vmap for file backed pages
- rebase to master
Changes from V2:
- fix buggy range overlapping check
- tear down MMU notifier during vhost ioctl to make sure
  invalidation request can read metadata userspace address and vq size
  without holding vq mutex.
Changes from V1:
- instead of pinning pages, use MMU notifier to invalidate vmaps
  and remap duing metadata prefetch
- fix build warning on MIPS

Jason Wang (6):
  vhost: generalize adding used elem
  vhost: fine grain userspace memory accessors
  vhost: rename vq_iotlb_prefetch() to vq_meta_prefetch()
  vhost: introduce helpers to get the size of metadata area
  vhost: factor out setting vring addr and num
  vhost: access vq metadata through kernel virtual address

 drivers/vhost/net.c   |   4 +-
 drivers/vhost/vhost.c | 850 ++++++++++++++++++++++++++++++++++++------
 drivers/vhost/vhost.h |  38 +-
 3 files changed, 766 insertions(+), 126 deletions(-)

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2.18.1