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madvise(2)							   madvise(2)



NAME

  madvise - Advise the system of the expected paging behavior of a process

SYNOPSIS

  #include <&lt;sys/types.h>&gt;
  #include <&lt;sys/mman.h>&gt;
  int madvise (
	  caddr_t addr,
	  size_t len,
	  int behav );

PARAMETERS

  addr	    Specifies the address of the region	to which the advice refers.

  len	    Specifies the length in bytes of the region	specified by the addr
	    parameter.

  behav	    Specifies the behavior of the region.  The following values	for
	    the	behav parameter	are defined in the sys/mman.h header file:

	    MADV_NORMAL
		      No further special treatment

	    MADV_RANDOM
		      Expect random page references

	    MADV_SEQUENTIAL
		      Expect sequential	references

	    MADV_WILLNEED
		      Will need	these pages

	    MADV_DONTNEED
		      Do not need these	pages

		      The system will free any whole pages in the specified
		      region.  All modifications will be lost and any swapped
		      out pages	will be	discarded.  Subsequent access to the
		      region will result in a zero-fill-on-demand fault	as
		      though it	is being accessed for the first	time.
		      Reserved swap space is not affected by this call.

	    MADV_SPACEAVAIL
		      Ensure that resources are	reserved

DESCRIPTION

  The madvise()	function permits a process to advise the system	about its
  expected future behavior in referencing a mapped file	or shared memory
  region.

NOTES

  Only a few values of the behav parameter values are operational on Tru64
  UNIX systems.	 Non-operational values	cause the system to always return
  success (zero).

RETURN VALUES

  Upon successful completion, the madvise() function returns zero.  Other-
  wise,	-1 is returned and errno is set	to indicate the	error.

ERRORS

  If the madvise() function fails, errno may be	set to one of the following
  values:

  [EINVAL]  The	behav parameter	is invalid.

  [ENOSPC]  The	behav parameter	specifies MADV_SPACEAVAIL and resources	can-
	    not	be reserved.

RELATED	INFORMATION

  Functions: mmap(2)