[PATCH v2 0/6] vhost: support upto 509 memory regions

[Igor Mammedov <imammedo@redhat.com>]

Ref to prefious version discussion:
[PATCH 0/5] vhost: support upto 509 memory regions
    http://www.spinics.net/lists/kvm/msg117654.html

Chagelog v1->v2:
  * fix spelling errors
  * move "vhost: support upto 509 memory regions" to the end of queue
  * move kvfree() form 1/6 to 2/6 where it belongs
  * add vhost module parameter to enable/disable translation caching

Series extends vhost to support upto 509 memory regions,
and adds some vhost:translate_desc() performance improvemnts
so it won't regress when memslots are increased to 509.

It fixes running VM crashing during memory hotplug due
to vhost refusing accepting more than 64 memory regions.

It's only host kernel side fix to make it work with QEMU
versions that support memory hotplug. But I'll continue
to work on QEMU side solution to reduce amount of memory
regions to make things even better.

Performance wise for guest with (in my case 3 memory regions)
and netperf's UDP_RR workload translate_desc() execution
time from total workload takes:

Memory      |1G RAM|cached|non cached
regions #   |  3   |  53  |  53
------------------------------------
upstream    | 0.3% |  -   | 3.5%
------------------------------------
this series | 0.2% | 0.5% | 0.7%

where "non cached" column reflects trashing wokload
with constant cache miss. More details on timing in
respective patches.

Igor Mammedov (6):
  vhost: use binary search instead of linear in find_region()
  vhost: extend memory regions allocation to vmalloc
  vhost: add per VQ memory region caching
  vhost: translate_desc: optimization for desc.len < region size
  vhost: add 'translation_cache' module parameter
  vhost: support upto 509 memory regions

 drivers/vhost/vhost.c | 105 ++++++++++++++++++++++++++++++++++++++------------
 drivers/vhost/vhost.h |   1 +
 2 files changed, 82 insertions(+), 24 deletions(-)

-- 
1.8.3.1