Re: [PATCH net-next V4 0/5] vhost: accelerate metadata access through vmap()

Michael S. Tsirkin
2019-01-23T13:58:07Z

On Wed, Jan 23, 2019 at 05:55:52PM +0800, 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.
>
> Test shows about 24% improvement on TX PPS. It should benefit other
> cases as well.

ok I think this addresses most comments but it's a big change and we
just started 1.1 review so to pls give me a week to review this ok?

> 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 (5):
> 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: access vq metadata through kernel virtual address
>
> drivers/vhost/net.c | 4 +-
> drivers/vhost/vhost.c | 441 +++++++++++++++++++++++++++++++++++++-----
> drivers/vhost/vhost.h | 15 +-
> mm/shmem.c | 1 +
> 4 files changed, 410 insertions(+), 51 deletions(-)
>
> --
> 2.17.1