ukernel complexity metrics

Espen Skoglund esk at
Thu Feb 24 15:52:44 CET 2005

[Jonathan S Shapiro]
> On Thu, 2005-02-24 at 09:15 +0100, Ronald Aigner wrote:
>> I disagree with the opinion that the complexity of a microkernel
>> should be measured by the number of its system-calls. I find it
>> rather complex to multiplex dozen flavours of IPC via one
>> systemcall.

> I am not sure quite what motivated this comment. We have argued in
> the EROS design that having exactly one system call ("invoke
> capability", in our case) is good, but not because it reduces
> microkernel complexity -- in fact, it complicates it.

Would also like to add that the reason for multiplexing all these
operations in the IPC mechanism is not really to reduce complexity.
We multiplex all these operations because the operations are similar
enough in nature to share the same codepath and thereby reduce the
cache/memory footprint of the kernel.

I don't think anyone has ever stated that the number of system calls
is a measure for the *complexity* of the kernel.


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