[ kvm-Bugs-1906204 ] AMD NPT causes performance degradation

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Bugs item #1906204, was opened at 2008-03-03 13:45
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Technologov (technologov)
Assigned to: Nobody/Anonymous (nobody)
Summary: AMD NPT causes performance degradation

Initial Comment:
Platform: F7/x64, AMD Barcelona K10, KVM-61.

Guest: Windows XP SP2.

By default, the new Nested Page Tables is enabled, which should accelerate guests.

While it *does* accelerate guests in some areas, particularly guest OS setup time dropped by 20% - which is great, but in other areas I see performance degradation.

For example:
Passmark PerformanceTest v6.1 shows
2D Graphics Marks: 78.6 (without NPT)

2D Graphics Marks: 18.9 (with NPT)

NPT was disabled using:
# rmmod kvm-amd
# modprobe kvm-amd npt=0
# dmesg | tail

and all the graphics feel more sluggish, and way slower.
I have used SDL rendering.

-Alexey, 03.03.2008.

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