madvise(2)							System Calls Manual							madvise(2)

NAME

       madvise() - advise the system of a process's expected paging behavior

SYNOPSIS

DESCRIPTION

       The system call permits a process to advise the system about its expected future behavior in referencing a mapped file, an anonymous memory
       region, or a shared memory region.  Certain implementations can use this information to optimize the use of resources.

       addr and len specify the address and length in bytes of the region to which the advice refers.  For the address and  length  must  be  con-
       tained within a successful call to (see mmap(2)) or a successful call to (see shmat(2)); otherwise, fails with an [EINVAL] error.

       The behav argument is one the following flags defined in the header
	      Removes  any  previous advice and sets the default behavior.  By default, the kernel tracks access patterns on data objects and per-
	      forms I/Os based on process trends (that is, sequential versus random).  Sequential trends cause	larger	"read-ahead"  I/Os,  while
	      random accesses reduce the amount of I/O to avoid unnecessary I/O.

	      Informs the kernel that any objects mapped in this range
		     will be accessed in a random matter.  The kernel will read only the minimal amount of data to satisfy the user fault.

	      Informs the kernel that any objects mapped in this range
		     will  be  accessed  in a sequential matter.  The kernel will perform the maximum read-ahead for every fault.  The kernel does
		     not pay attention to access patterns and trends, but instead assumes sequentiality for every access on the object.

	      Informs the kernel that the specified range
		     is no longer needed by the process.  This allows the kernel to release the physical pages associated with	an  address  range
		     back to the system for use by other processes.

		     is  restricted to object ranges created with calls to and Attempting to use on an object that was not created using a call to
		     or will result in [EINVAL] being returned to the caller.

	      Will need these pages.

	      Ensure that resources are reserved.

WARNINGS

       The current implementation of defines and as null operations.

RETURN VALUE

       returns the following values:

	      Successful completion.
	      Failure.
		     is set to indicate the error.

ERRORS

       If fails, is set to one of the following values.

	      [EFAULT]	     The range specified by (addr, addr+len) is invalid for a process's address space, or permission was incorrect on  the
			     object for the behav specified.

	      [EINVAL]	     behav contains an invalid value, or addr is not a multiple of the page size as returned by the system call

	      [EINVAL]	     The address range specified by addr and len was not created by a successful call to or

AUTHOR

       was developed by HP and OSF.

SEE ALSO

       mmap(2), sysconf(2).

STANDARDS CONFORMANCE

																	madvise(2)