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freebsd/sys/dev/xen/blkfront
Roger Pau Monné ee74891fc7 blkfront: add support for unmapped IO
Using unmapped IO is really beneficial when running inside of a VM,
since it avoids IPIs to other vCPUs in order to invalidate the
mappings.

This patch adds unmapped IO support to blkfront. The following tests
results have been obtained when running on a Xen host without HAP:

PVHVM
     3165.84 real      6354.17 user      4483.32 sys
PVHVM with unmapped IO
     2099.46 real      4624.52 user      2967.38 sys

This is because when running using shadow page tables TLB flushes and
range invalidations are much more expensive, so using unmapped IO
provides a very important performance boost.

Sponsored by:	Citrix Systems R&D
MFC after:	2 weeks
X-MFC-with:	r289834
2015-10-23 15:46:42 +00:00
..
blkfront.c blkfront: add support for unmapped IO 2015-10-23 15:46:42 +00:00
block.h Add support for Xen blkif indirect segment I/Os. This makes it possible for 2015-07-30 03:50:01 +00:00