DOCUMENT ID:  1204-02

SYNOPSIS:     Layers of the Virtual Memory System

OS RELEASE:   2.4

PRODUCT:      Solaris

KEYWORDS:     layers virtual memory address space segment vnode driver


DESCRIPTION:

Layers of the Virtual Memory System


SOLUTION:

*       SunOS system calls and services - the user interface to
        the kernel's VM management structures and procedures. 
        The predominant system call is mmap(), and read() and 
        write() calls are implemented through an internal version
        of mmap().

*       Address space - state information about a process's address 
        space is maintained through a linked list of contiguous
        address mappings arranged by virtual address.

*       Segment drivers - the address space mappings are termed
        segments, and operations on segments are implemented
        through a set of segment drivers.

*       vnode drivers - the vnode object managers are responsible
        for creating and initializing a request page, which may 
        include interfacing with the physical I/O layer to obtain
        the data.

*       Physical I/O - the machine-dependent layer that manages
        backing store according to the physical characteristics 
        of the peripheral device.

*       Hardware address translation (HAT) - the HAT layer is 
        the machine-dependent code that manages the hardware
        translations to pages in the machine's MMU.


DATE APPROVED: 09/18/95