The Design and Implementation of the Anykernel and Rump Kernels

A–16
RUMP(3) NetBSD Library Functions Manual RUMP(3)
Clients using services provided by rump kernels can exist either in the
same process as the rump kernel or in other processes. Local clients
access the rump kernel through direct function calls. They also naturally
have access to the kernel memory space. This document is geared
towards local clients. For more information on remote clients, see
rump_sp(7). It is also possible to use unmodified application binaries
as remote clients with rumphijack(3).
A rump kernel is bootstrapped by calling rump_init(). Before bootstrapping
the kernel, it is possible to control its functionality by setting
various environment variables:
RUMP_NCPU
If set, indicates the number of virtual CPUs configured
into a rump kernel. The default is the number of host
CPUs. The number of virtual CPUs controls how many
threads can enter the rump kernel simultaneously.
RUMP_VERBOSE
If set to non-zero, activates bootverbose.
RUMP_THREADS
If set to 0, prevents the rump kernel from creating any
kernel threads. This is possible usually only for file
systems, as other subsystems depend on threads to work.
RUMP_MEMLIMIT
If set, indicates how many bytes of memory a rump kernel
will allocate before attempting to purge caches. The
default is as much as the host allows.
RUMP_NVNODES
Sets the value of the kern.maxvnodes sysctl node to the
indicated amount. Adjusting this may be useful for
example when testing vnode reclaim code paths. While
the same value can be set by means of sysctl, the env
NetBSD 5.99.48 March 25, 2011 NetBSD 5.99.48