Why does perfmon on Windows report very high exception dispatches per second

I am running a Java web server and occasionally I see high keel cpu and the machine pauses for a number of seconds.

During this time network activity, interrupts, context switches all drop off but the perfmon counter "System/Exception dispatches per second" becomes very high and correlates exactly with the period of high CPU.

Exceptions in java code do not appear to map to this counter and instead show up as user mode cpu so it doesn't seem to be caused by the Web server code using java exceptions. What could be causing all the windows exceptions?

If windows runs out of some resource does it cause this counter to increase?

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