NAME

vadvise − give advice to paging system

SYNOPSIS

vadvise(param)

DESCRIPTION

Vadvise is used to inform the system that process paging behavior merits special consideration.  Parameters to vadvise are defined in the file <vadvise.h> .  Currently, two calls to vadvise are implemented:

The call

vadvise(VA_ANOM);

advises that the paging behavior is not likely to be well handled by the system’s default algorithm, since reference information collected over macroscopic intervals (e.g. 10-20 seconds) will not serve to indicate future page references.  The system in this case will choose to replace pages with little emphasis placed on recent usage, and more emphasis on referenceless circular behavior.  It is essential that processes which have very random paging behavior (such as LISP during garbage collection of very large address spaces) call vadvise, as otherwise the system has great difficulty dealing with their page-consumptive demands. 

The call

vadvise(VA_NORM);

restores default paging replacement behavior after a call to

vadvise(VA_ANOM);

BUGS

This call is peculiar to this version of UNIX.  The options and specifications of this system call and even the call itself are expected to change.  It is expected to be extended with additional facilities in future versions of the system.  In particular it is expected that this call will be particular to a segment, and that other behaviors such as sequential behavior will be specifiable. 

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