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

NAME
     mmaaddvviissee, ppoossiixxmmaaddvviissee - give advice about use of memory

SYNOPSIS
     ##iinncclluuddee <>

     int
     mmaaddvviissee(void *addr, sizet len, int advice);

     int
     ppoossiixxmmaaddvviissee(void *addr, sizet len, int advice);

DESCRIPTION
     The mmaaddvviissee() 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
     specified in advice can only be one of the following values:

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

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

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

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

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

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

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

     POSIXMADVWILLNEED
                      Same as MADVWILLNEED but used with ppoossiixxmmaaddvviissee() sys-
                      tem call.

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

     POSIXMADVDONTNEED
                      Same as MADVDONTNEED but used with ppoossiixxmmaaddvviissee() sys-
                      tem call.

     MADVFREE        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 mmaaddvviissee() system call.

     The ppoossiixxmmaaddvviissee() behaves same as mmaaddvviissee() except that it uses values
     with POSIX prefix for the advice 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.

EERRRROORRSS
     mmaaddvviissee() fails if one or more of the following are true:

     [EINVAL]           The value of advice is incorrect.

     [EINVAL]           The address range includes unallocated regions.

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

LEGACY SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>

     int
     mmaaddvviissee(caddrt addr, sizet len, int advice);

     int
     ppoossiixxmmaaddvviissee(caddrt addr, sizet len, int advice);

     The include file  is necessary.  The type of addr has
     changed.

SEE ALSO
     mincore(2), minherit(2), mprotect(2), msync(2), munmap(2), compat(5)

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

BSD                              June 9, 1993                              BSD