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1 | .\" Copyright (c) 1980 Regents of the University of California. |
2 | .\" All rights reserved. The Berkeley software License Agreement | |
3 | .\" specifies the terms and conditions for redistribution. | |
4 | .\" | |
5 | .\" @(#)vadvise.2v 4.1 (Berkeley) %G% | |
6 | .\" | |
7 | .TH VADVISE 2V | |
8 | .UC 4 | |
9 | .SH NAME | |
10 | vadvise \- give advice to paging system | |
11 | .SH SYNOPSIS | |
12 | .B vadvise(param) | |
13 | .SH DESCRIPTION | |
14 | .I Vadvise | |
15 | is used to inform the system that process paging behavior merits special | |
16 | consideration. Parameters to | |
17 | .I vadvise | |
18 | are defined in the file | |
19 | .B <vadvise.h> . | |
20 | Currently, two calls to | |
21 | .I vadvise | |
22 | are implemented: | |
23 | .PP | |
24 | The call | |
25 | .IP | |
26 | .B "vadvise(VA_ANOM);" | |
27 | .LP | |
28 | advises that the paging behavior is not likely to | |
29 | be well handled by the system's default algorithm, since reference information | |
30 | collected over macroscopic intervals (e.g. 10-20 seconds) | |
31 | will not serve to indicate future page references. The system in this case | |
32 | will choose to replace pages with little emphasis placed on recent usage, | |
33 | and more emphasis on referenceless circular behavior. It is \fIessential\fR | |
34 | that processes which have very random paging behavior (such as | |
35 | LISP during garbage collection of very large address spaces) call | |
36 | .I vadvise, | |
37 | as otherwise the system has great difficulty dealing with their | |
38 | page-consumptive demands. | |
39 | .PP | |
40 | The call | |
41 | .IP | |
42 | .B "vadvise(VA_NORM);" | |
43 | .LP | |
44 | restores default paging replacement behavior after a call to | |
45 | .IP | |
46 | .B "vadvise(VA_ANOM);" | |
47 | .SH BUGS | |
48 | This call is peculiar to this version of UNIX. | |
49 | The options and specifications of this system call and even the call itself | |
50 | are expected to change. It is expected to be extended with additional | |
51 | facilities in future versions of the system. In particular it is expected | |
52 | that this call will be particular to a segment, and that other behaviors | |
53 | such as sequential behavior will be specifiable. |