The Design and Implementation of the Anykernel and Rump Kernels

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Anecdotal analysis
For several weeks the author did his day-to-day web browsing with Firefox acting as
a remote client for a rump kernel TCP/IP stack. There was no human-perceivable
difference between the performance of a rump networking stack and the host networking
stack, either in bulk downloads of speeds up to 10Mbps, flash content or
interactive page loads. The only human-perceivable difference was the ability to reboot
the TCP/IP stack from under the browser without having to close the browser
first.
Microbenchmarks show that remote system calls are orders of magnitude slower than
local system calls especially due to copyin/out I/O. However, this“macrobenchmark”
suggests that others factors in real application hugely mitigate this performance difference.
We conclude that without a specific application use case any optimizations
are premature. In the event of such use cases emerging, optimizations know from
literature [14, 63] may be attempted.
3.13 Summary
We began this chapter by describing the cornerstone techniques for how to convert
an existing monolithic kernel codebase into an anykernel. To retain the existing
properties of the monolithic kernel, we did not introduce any new technologies,
and adjusted the codebase using the following techniques: code moving, function
pointers and weak symbols. These techniques were enough to convert the NetBSD
kernel into an anykernel with an independent base and orthogonal factions.
We went over the various rump kernel implementation aspects such as implicit thread
creation and the CPU scheduler.
After that, we studied the effects that feature