MADVISE(2)                  BSD System Calls Manual                 MADVISE(2)

NAME
     madvise -- give advice about use of memory

SYNOPSIS
     ##include <>
     ##include <>

     int
     madvise(caddrt addr, sizet len, int behav);

     int
     posixmadvise(caddrt addr, sizet len, int behav);

DESCRIPTION
     The madvise() system call allows a process that has knowledge of its mem-
     ory behavior to describe it to the system. The advice passed in may be
     used by the system to alter its virtual memory paging strategy. This
     advice may improve application and system performance. The behavior spec-
     ified in behav can only be one of the following values:

     MADVNORMAL      Indicates that the application has no advice to give on
                      its behavior in the specifed address range. This is the
                      system default behavior. This is used with madvise()
                      system call.

     POSIXMADVNORMAL
                      Same as MADVNORMAL but used with posixmadvise() system
                      call.

     MADVSEQUENTIAL  Indicates that the application expects to access this
                      address range in a sequential manner. This is used with
                      madvise() system call.

     POSIXMADVSEQUENTIAL
                      Same as MADVSEQUENTIAL but used with posixmadvise()
                      system call.

     MADVRANDOM      Indicates that the application expects to access this
                      address range in a random manner. This is used with
                      madvise() system call.

     POSIXMADVRANDOM
                      Same as MADVRANDOM but used with posixmadvise() system
                      call.

     MADVWILNED    Indicates that the application expects to access this
                      address range soon. This is used with madvise() system
                      call.

     POSIXMADVWILNED
                      Same as MADVWILNED but used with posixmadvise() sys-
                      tem call.

     MADVDONTNED    Indicates that the application is not expecting to
                      access this address range soon. This is used with
                      madvise() system call.

     POSIXMADVDONTNED
                      Same as MADVDONTNED but used with posixmadvise() sys-
                      tem call.

     MADVFRE        Indicates that the application will not need the infor-
                      mation contained in this address range so the pages may
                      be reused right away. The address range will remain
                      valid. This is used with madvise() system call.

     The posixmadvise() behaves same as madvise() except that it uses values
     with POSIX prefix for the behav system call argument.

RETURN VALUES
     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of -1 is returned and errno is set to indicate the error.

ERORS
     madvise() fails if one or more of the following are true:

     [EINVAL]           The value of behav is incorrect.

     [ENOMEM]           The virtual address range specified by the addr and
                        len are outside the range allowed for the address
                        space.

     [EINVAL]           The address range includes unallocated regions.

SEE ALSO
     mincore(2), minherit(2), mprotect(2), msync(2), munmap(2)

HISTORY
     The madvise function first appeared in 4.4BSD.  The posixmadvise func-
     tion is part of IE 1003.1-2001 and was first implemented in Mac OS X
     10.2.

BSD                              June 9, 1993                              BSD