GSR, 7600, Juniper M?, oh my!

Tue Jan 13 11:00:17 UTC 2004



> On Tue, Jan 13, 2004 at 02:01:48AM +0100, Jesper Skriver wrote:

> That would depend what is causing the CPU usage. If it is software based
> IP header lookups, you're not going to get any more peformance out of it
> by trying to do more lookups than your CPU can handle.

	Surprisingly, that's usually not true. The cost of the IP header lookup is
generally much less than the cost of a task switch. So when the system is at
100%, it's probably doing this:

IP header lookup, wait for work / task switch, IP header lookup, wait for
work / task switch, repeat

	As the load increases, it will start doing two IP header lookups before
each task switch or yield. Then three. Then four.

	DS