[Qemu-devel] [RFC PATCH 00/11] speedup vring processing with MemoryRegionCaches

[Paolo Bonzini]

It is known that virtio's usage of ld_*_phys and st_*_phys functions
wastes time in address_space_translate, visiting the
AddressSpaceDispatch's radix tree.

This series introduces a small cache that changes these functions
to a simple range check and memory access.  The effect is a bit
underwhelming, because the improvement is only 1-2Kiops/second.
Nevertheless I'm throwing out the patches so that for example they
can be tested on s390.

Things to fix: handle address_space_cache_init failures
in virtio_init_region_cache.  Also, once virtio breaks free of
address_space_memoory, we'll need to handle invalidation in IOMMU regions.
For the latter, maybe it's worth introducing a new abstraction that
is higher-level than MemoryListener and covers both regular and IOMMU
memory regions.

Paolo

Paolo Bonzini (11):
  exec: optimize remaining address_space_* cases
  exec: introduce memory_ldst.inc.c
  exec: introduce address_space_extend_translation
  exec: introduce MemoryRegionCache
  virtio: make virtio_should_notify static
  virtio: add virtio_*_phys_cached
  virtio: use address_space_map/unmap to access descriptors
  virtio: use MemoryRegionCache to access descriptors
  virtio: add MemoryListener to cache ring translations
  virtio: use VRingMemoryRegionCaches for descriptor ring
  virtio: use VRingMemoryRegionCaches for avail and used rings

 exec.c                            | 687 +++++-------------------------------
 hw/net/virtio-net.c               |  14 +-
 hw/virtio/virtio.c                | 322 +++++++++++++----
 include/exec/cpu-all.h            |  23 ++
 include/exec/cpu-common.h         |  15 -
 include/exec/memory.h             | 166 +++++++++
 include/hw/virtio/virtio-access.h |  52 +++
 include/hw/virtio/virtio.h        |   2 +-
 include/qemu/typedefs.h           |   1 +
 memory_ldst.inc.c                 | 709 ++++++++++++++++++++++++++++++++++++++
 10 files changed, 1316 insertions(+), 675 deletions(-)
 create mode 100644 memory_ldst.inc.c

-- 
1.8.3.1