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 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 | 416 +++++++++++++++++++++++++++++++++++++----- drivers/vhost/vhost.h | 15 +- 3 files changed, 384 insertions(+), 51 deletions(-) -- 2.17.1
