The Design and Implementation of the Anykernel and Rump Kernels

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runtime (s)
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
none hv base base+hv
Figure 3.1: Performance of position independent code (PIC). A regular
kernel is compiled as non-PIC code. This compilation mode is effectively the same
as “none” in the graph. If the hypervisor and rump kernel base use PIC code, the
execution time increases as is expected. In other words, rump kernels allow to make
a decision on the tradeoff between execution speed and memory use.
to create and disband 300k threads in a rump kernel. As can be deduced from
the combinations, shared and static libraries can be mixed in a single rump kernel
instance so as to further optimize the behavior with the memory/CPU tradeoff.
3.2 Running the Kernel in an Hosted Environment
Software always runs on top of an entity which provides the interfaces necessary for
the software to run. A typical operating system kernel runs on top of hardware and
uses the hardware’s “interfaces” to fulfill its needs. When running on top a hardware
emulator the emulator provides the same hardware interfaces. In a paravirtualized
setup the hypervisor provides the necessary interfaces. In a usermode OS setup, the
application environment of the hosting OS makes up the hypervisor. In this section
we discuss hosting a rump kernel in a process on a POSIX host.