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madvise(2)
NAME
  madvise - Advise the system of the expected paging behavior of a process

SYNOPSIS
  #include <sys/types.h>
  #include <sys/mman.h>
  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 DIGITAL
  UNIX systems.	 Non-operational values cause the system to always return
  success (zero).

RETURN VALUES
  Upon successful completion, the madvise() function returns zero.
  Otherwise, -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
	    cannot be reserved.

RELATED INFORMATION
  Functions: mmap(2)