[c-nsp] High CPU utilisation when using RSPAN on 4500s

[Ras]

We've recently found that using RSPAN on our 4500s seems to absolutely
kill the CPU. If we're RSPANing 5-10Mb/s of traffic, the CPU hits 100%
and OSPF/BGP/PIM/HSRP etc start having timeouts and all sorts of
problems.

Is this a known effect of RSPAN or is something misconfigured somewhere?

Even switches that are nominally just in the forwarding path (ie not
source or sink of RSPAN traffic) are getting hit by this.

Thanks,
Ras