Hi everyone,
I understand BVT is not the default scheduler anymore, but perhaps
this would be of interest to some people. Some changes in the current
BVT scheduler compared to the BVT code in Xen 3.0 has affected its
correctness.
In the original (Xen 3.0) BVT scheduler the weights resulted in
correct CPU allocations. However, the current BVT scheduler (CS
10647:8e55c5c11475) does not do it properly.
Here is the outcome of the weights for CPU allocation in the original
(Xen 3.0) BVT scheduler and the current BVT scheduler when Dom0 and
Dom1 run pure CPU intensive tasks (slurp program).
Xen 3.0 BVT Current BVT
Dom 0 Dom 1 Dom 0 Dom 1
---------------------------------------------------------------
weights 10 10 10 10
CPU Util 50% 50% 50% 50%
---------------------------------------------------------------
weights 10 20 10 20
CPU Util 66.6% 33.3% 60% 40%
---------------------------------------------------------------
weights 10 30 10 30
CPU Util 75% 25% 67% 33%
---------------------------------------------------------------
weights 10 40 10 40
CPU Util 80% 20% 70% 30%
---------------------------------------------------------------
weights 10 50 10 50
CPU Util 83% 16.6% 72.7% 26.6%
---------------------------------------------------------------
weights 10 60 10 60
CPU Util 85.6% 14.3% 75% 25%
---------------------------------------------------------------
weights 10 70 10 70
CPU Util 87.4% 12.5% 77% 23%
---------------------------------------------------------------
CPU utilization were obtained using ''xentop''.
Does anyone know which new changes might have caused this anomaly? I
ran ''hg annotate'' on sched_bvt.c and it looks like most of the
algorithm specific code has not been touched in a while.
Thanks,
Diwaker
--
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