excessive load on host after upgrading from 3.1 to 3.2

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Host: Ubuntu 10.04, 16 cores, 32GB

13 Guests, various types of Linux

With all versions of 3.1 the load on host was mostly around 0.5 with spikes when the guests were active.

After upgrading to 3.2 the load has suddenly increased to 5+. The step on the attached chart is exactly at the hour I've upgraded VB. I went through all 3.2 releases but the load is always high. The guests are doing exactly what they did before, but even when idle the CPU SYS component is high in the guests (70-80%), and the corresponding host processes also use quite a lot of CPU.

I've tried even binding the host processes on particular CPUs using taskset but it doesn't change anything on the charts.

I'm attaching the history of load and of the CPU usage on the host. If you need more details please let me know.

[costing]

load on host, before and after the upgrade

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cpu usage on host, before and after the upgraed

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one of the log files