projects / unix-history / blame
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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. |