|author||Roger Pau Monné <royger@FreeBSD.org>||2014-08-11 15:37:02 +0000|
|committer||Roger Pau Monné <royger@FreeBSD.org>||2014-08-11 15:37:02 +0000|
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 Tested by: robak MFC after: 1 week PR: 191173 dev/xen/blkfront/blkfront.c: - Add and announce support for unmapped IO.
Notes: svn path=/head/; revision=269814
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