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

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

[SourceForge.net]

Bugs item #1906204, was opened at 2008-03-03 13:45
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

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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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https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

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

[SourceForge.net]

Bugs item #1906204, was opened at 2008-03-03 12:45
Message generated for change (Comment added) made by markit
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
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.

----------------------------------------------------------------------

Comment By: Marco Menardi (markit)
Date: 2008-08-26 21:59

Message:
Logged In: YES 
user_id=113918
Originator: NO

Same here, XP has a noticeable slow down. Was faster with my AMD X2 that
is with 4 core Phenom. WIth npt=0 is fast again (as with X2 or better).
Tried with kvm 70...73, debian Sid 64 as host

----------------------------------------------------------------------

Comment By: Anthony Liguori (aliguori)
Date: 2008-03-24 23:03

Message:
Logged In: YES 
user_id=120449
Originator: NO

I am able to reproduce this although the results aren't as extreme.  The
biggest impact is coming from the passmark 2D Graphics Filled Rectangles
test.  Only about 40k exits are occurring while this benchmark is being
run.  It's not impacted by the use of large pages.  Still investigating.


----------------------------------------------------------------------

Comment By: Technologov (technologov)
Date: 2008-03-03 16:25

Message:
Logged In: YES 
user_id=1839746
Originator: YES

Yes, those numbers are always reproducible, even with reloading KVM base
module too.

Just try it for yourself, the benchmark is shareware (free for 30 days) -
but VMs rarely live any longer  anyways :)

link:
http://www.passmark.com/

-Alexey, 03.03.2008.

----------------------------------------------------------------------

Comment By: Joerg Roedel (jroedel)
Date: 2008-03-03 15:40

Message:
Logged In: YES 
user_id=2019182
Originator: NO

Reloading the KVM-AMD module does not disable NPT completly. You have to
reload the KVM base module too. Can you reproduce your numbers if you
reload both and disable NPT?

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

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

[SourceForge.net]

Bugs item #1906204, was opened at 2008-03-03 13:45
Message generated for change (Comment added) made by avik
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
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.

----------------------------------------------------------------------

>Comment By: Avi Kivity (avik)
Date: 2008-08-27 14:41

Message:
Logged In: YES 
user_id=539971
Originator: NO

Make sure your host has the latest BIOS.

----------------------------------------------------------------------

Comment By: Marco Menardi (markit)
Date: 2008-08-26 22:59

Message:
Logged In: YES 
user_id=113918
Originator: NO

Same here, XP has a noticeable slow down. Was faster with my AMD X2 that
is with 4 core Phenom. WIth npt=0 is fast again (as with X2 or better).
Tried with kvm 70...73, debian Sid 64 as host

----------------------------------------------------------------------

Comment By: Anthony Liguori (aliguori)
Date: 2008-03-25 00:03

Message:
Logged In: YES 
user_id=120449
Originator: NO

I am able to reproduce this although the results aren't as extreme.  The
biggest impact is coming from the passmark 2D Graphics Filled Rectangles
test.  Only about 40k exits are occurring while this benchmark is being
run.  It's not impacted by the use of large pages.  Still investigating.


----------------------------------------------------------------------

Comment By: Technologov (technologov)
Date: 2008-03-03 17:25

Message:
Logged In: YES 
user_id=1839746
Originator: YES

Yes, those numbers are always reproducible, even with reloading KVM base
module too.

Just try it for yourself, the benchmark is shareware (free for 30 days) -
but VMs rarely live any longer  anyways :)

link:
http://www.passmark.com/

-Alexey, 03.03.2008.

----------------------------------------------------------------------

Comment By: Joerg Roedel (jroedel)
Date: 2008-03-03 16:40

Message:
Logged In: YES 
user_id=2019182
Originator: NO

Reloading the KVM-AMD module does not disable NPT completly. You have to
reload the KVM base module too. Can you reproduce your numbers if you
reload both and disable NPT?

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

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

[SourceForge.net]

Bugs item #1906204, was opened at 2008-03-03 12:45
Message generated for change (Comment added) made by markit
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
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.

----------------------------------------------------------------------

Comment By: Marco Menardi (markit)
Date: 2008-08-29 01:11

Message:
Logged In: YES 
user_id=113918
Originator: NO

Latest bios flashed, but still performances issues. Only with npt=0 is
noticeable faster
(btw, tested with guest at res 1680x1050 or 1920x1200, at full screen or
not)

----------------------------------------------------------------------

Comment By: Avi Kivity (avik)
Date: 2008-08-27 13:41

Message:
Logged In: YES 
user_id=539971
Originator: NO

Make sure your host has the latest BIOS.

----------------------------------------------------------------------

Comment By: Marco Menardi (markit)
Date: 2008-08-26 21:59

Message:
Logged In: YES 
user_id=113918
Originator: NO

Same here, XP has a noticeable slow down. Was faster with my AMD X2 that
is with 4 core Phenom. WIth npt=0 is fast again (as with X2 or better).
Tried with kvm 70...73, debian Sid 64 as host

----------------------------------------------------------------------

Comment By: Anthony Liguori (aliguori)
Date: 2008-03-24 23:03

Message:
Logged In: YES 
user_id=120449
Originator: NO

I am able to reproduce this although the results aren't as extreme.  The
biggest impact is coming from the passmark 2D Graphics Filled Rectangles
test.  Only about 40k exits are occurring while this benchmark is being
run.  It's not impacted by the use of large pages.  Still investigating.


----------------------------------------------------------------------

Comment By: Technologov (technologov)
Date: 2008-03-03 16:25

Message:
Logged In: YES 
user_id=1839746
Originator: YES

Yes, those numbers are always reproducible, even with reloading KVM base
module too.

Just try it for yourself, the benchmark is shareware (free for 30 days) -
but VMs rarely live any longer  anyways :)

link:
http://www.passmark.com/

-Alexey, 03.03.2008.

----------------------------------------------------------------------

Comment By: Joerg Roedel (jroedel)
Date: 2008-03-03 15:40

Message:
Logged In: YES 
user_id=2019182
Originator: NO

Reloading the KVM-AMD module does not disable NPT completly. You have to
reload the KVM base module too. Can you reproduce your numbers if you
reload both and disable NPT?

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=1906204&group_id=180599