Re: [Xen-devel] Serious performance issues

[Tommi Virtanen <tv@xxxxxxxxxxxxx>]

Ian Pratt wrote:
> Have you got some interrupt line going crazy?
That seems to be the problem.

In native linux, I see:

0       timer   1000/s
LOC             1000/s

and in xen dom0 I see:

21      uhci_hcd        35000/s
130     timer           45000/s

rmmodding uhci_hcd removes irq 21, but makes the timer
speed up to 115000/s.

rmmod ohci13943, rmmod ehci_hcd makes the timer go
800000/s.

rmmoding even more drivers puts the peak at 1100000/s,
until it suddenly drops to 30/s. Didn't check between each
rmmod, so I don't know which exact one caused it.

Unplugging my USB trackball and modprobing _all_ of the drivers above
causes timer to tick at 60/s. Plugging in my USB trackball makes it
33000/s. Unplugging has no effect.

Booting up with trackball unconnected gives about 30000/s, too, so
it's not just the USB mouse driver. It seems there is a problem with
USB.

But that doesn't explain everything. It seems the bridge module has
trouble, too. rmmod bridge, or just ip li set dev br0 down makes timer
go from crazy to normal, too.

Thanks for the hint, I think I can manage to find a working
configuration based on this. Of course, having no such problems in the
first place would be even better.


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