[Xen-devel] Xen Domains scheduling parameters do not take effect before rebooting

[Priya <pbhat@xxxxxxxxxxxx>]

Dear all,

I am not observing a change in the performance of my hardware-assisted virtual machines (HVMs) when I change the scheduling parameters (weight and cap) associated with the HVMs unless they are rebooted. 

I am testing using 2 HVMs running Linux kernels (2.6.24-26-generic) in the guest operating system. My hardware is 1 x Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz. I have pinned my Domain-0 to physical CPU-0 and the 2 HVMs to physical CPU-1. In order create a load on my HVMs I run the "glxgears" API and monitor the performance using "xentop" (and from the movement of the gears, on the pop-up screen). I use the "xe" CLI to set and check the scheduling parameters.

I have experimented with setting the cap and weight of one domains to the least  possible value (1, 1 respectively) and that of the other to the maximum possible value (0 and 65536 respectively), the initial cap and weight of both domains being at the default setting of 0 and 256, but the processor utilization remains unchanged (at 50% for both domains) unless I reboot my HVMs. Once I do that, I can see the expected (enormous) difference in the performance.

Is it not possible to change processor utilization without having to reboot the HVMs? What am I missing here?

Please help!

--
Priya Bhat

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