high load and high CPU used by sy (system mode)

Hello community. We have an ODA in virtualized mode.

In one ODA_BASE node we have spotted a rising load average that reached the value of 400 (some days ago, the similar situation raised on the other node, reaching the value of 600, so we rebooted the node due without investigating).

Using top command, there were not so much processes eating CPU time (I mean, something normal).

But top reported an high "sy" usage. As far as I can understand it is the kernel eating CPU time.

top - 14:53:27 up 79 days, 4:29, 7 users, load average: 443.15, 445.96, 445.92  Tasks: 2487 total, 443 running, 2044 sleeping, 0 stopped, 0 zombie  Cpu(s): 9.1%us, 89.4%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 1.5%st  Mem: 204012220k total, 196283004k used, 7729216k free, 1354832k buffers  Swap: 19528700k total, 175068k used, 19353632k free, 67472212k cached