[Xen-users] Performance issue with blktap2?

[Nathan March <nathan@xxxxxxxxxxxxxxxxxxxx>]

 Everything I've read online indicates that I should expect equal or 
greater performance from the blktap drivers instead of file access, 
unfortunately this isn't the case on my test machine
 - Dual Xeon L5640, dom0 pinned to 1 cpu backed by a netapp nfs mount.
 - Dom 0 running a recent checkout (last day or two) from 
xen-4.0-testing with the pvops kernel from Jeremy's testing (2.6.31.13)
 - Dom U running 2.6.32.8

Times indicated are from "time bonnie++ -u 1":

file inside the dom0 (mount -o loop):

file inside a vm:
    2m40.515s, 2m38.181s, 2m31.788s, 2m34.391s, 2m35.671s
tap:aio inside the dom0 (tapdisk2 -n and then mounting it):
    3m23.040s, 3m19.900s, 3m15.406s, 3m15.594s, 3m14.867s
tap:aio inside a vm:
    3m54.694s, 3m49.185s, 3m50.864s, 3m57.644s, 4m1.372s

Any thoughts? That's nearly a 50% performance hit..

Thanks!

- Nathan

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