[Bridge] Increase on context switches

[Fabian Ischia]

I've started using bridges at the office because I need to connect Virtual Machines (User-Mode-Linux). I've noticed that it causes a huge increase in context switches.
The context switches seem to be limited somehow (I guess some kernel mechanism to prevent going wild). The context switches, even though they're cheap, also account for some 8-10% of CPU.
I've checked with some more knowledgeable people than me and they said in a heavy loaded server I should expect something around 30K but I'm around 1M and that's with the machine just sitting idle.
Does anyone know if there is an actual bug, and the appropriate patch to fix it; or whether it is considered OK this behavior? 

Fabian

Running vmstat I see:
Without bridges:
  1  0 187312  58088  32144 338636    0    0     0     0  189  997 83  1 17  0
 1  0 187312  57948  32144 338636    0    0     0     0  140  576 25  1 74  0
 1  0 187312  58088  32144 338636    0    0     0     0  168  777 83  1 17  0
 1  0 187312  58016  32144 338636    0    0     0     0  154  655 26  1 73  0
 1  0 187312  57960  32144 338636    0    0     0     0  137  500 82  1 17  0
 1  0 187312  58088  32144 338636    0    0     0     0  154  611 25  1 74  0
 1  0 187312  57960  32144 338636    0    0     0     0  135  525 83  1 17  0

With 4 bridges idle (no traffic on the interfaces)
 1  0 187312  50864  32276 338632    0    0     0     0  139 134920 81  4 15  0
 1  0 187312  51012  32276 338632    0    0     0     0  178 145827 24  3 72  0
 1  0 187312  50880  32276 338632    0    0     0    36  180 152482 82  3 16  0
 1  0 187312  50808  32276 338636    0    0     0     0  145 126225 25  2 72  0
 1  0 187312  50888  32284 338628    0    0     0    56  162 136169 82  2 16  0
 1  0 187312  50820  32284 338636    0    0     0     0  207 112448 26  3 71  0
 1  0 187312  50740  32284 338636    0    0     0     0  148 163085 82  4 15  0

The precedent metrics are from my desktop machine, on the actual host where I have more bridges.
 0  0      0 679748  34448 2404840    0    0     0     0   67 928669  3 10 86  0
 0  0      0 679748  34448 2404840    0    0     0     0   89 884379  2  9 90  0
 0  0      0 679748  34448 2404840    0    0     0     0   66 924828  2 10 88  0
 0  0      0 679748  34456 2404840    0    0     0     4   67 906076  5  8 87  0
 0  0      0 679748  34456 2404840    0    0     0     0   67 920194  1  9 91  0
 0  0      0 679748  34456 2404840    0    0     0     0   89 905816  1  11 91  0
 0  0      0 679748  34464 2404840    0    0     0     0   87 868858  3  10 91  0


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