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Pages and nodes
The microkernel provides some fixed number of pages
and nodes. There are typically many thousands of
pages and nodes. A page holds 4096 bytes of data and a node has
sixteen slots. A node also has an associated process-running
predicate which is TRUE if and only if the node is the
distinguished node of a running domain. Pages and nodes are
microkernel-implemented objects and they are accessed by keys.
Permanent state-bearing objects are ultimately built of pages and
nodes. Pages and nodes carry all of the permanent state of the
system. Pages and nodes are swapped by the microkernel to provide
a single-level store. Pages and nodes are the only primitive
microkernel objects provided in large numbers. The checkpoint-
restart mechanism and checkpoint to magnetic tape deal only with
pages and nodes.
A node key designates a node and provides authority
to retrieve keys from the node or to place keys into the node. A
fetch key also designates a node but may be used only to
retrieve keys from the node.
A page may be designated by read-write and read-only
page keys.
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