mctl(3B)

memory management control

From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.

NAME

mctl - memory management control

SYNOPSIS

cc [ flag... ] file ...  -lucb
#include <sys/types.h>
#include <sys/mman.h>

mctl(caddr_t addr, size_t len, int function, void *arg);

DESCRIPTION

mctl applies a variety of control functions over pages identified by the mappings established for the address range [addr, addr + len). The function to be performed is identified by the argument function. Valid functions are defined in mman.h as follows.

MC_LOCK

Lock the pages in the range in memory. This function is used to support mlock. See mlock(3) for semantics and usage. arg is ignored.

MC_LOCKAS
     Lock the pages in the address  space  in  memory.  This
     function  is used to support mlockall.  See mlockall(3)
     for semantics and usage.  addr  and  len  are  ignored.
     arg is an integer built from the flags:
               MCL_CURRENT   Lock current mappings
               MCL_FUTURE    Lock future mappings

MC_SYNC
     Synchronize the pages in the range with  their  backing
     storage.   Optionally  invalidate  cache  copies.  This
     function is used to support msync.   See  msync(3)  for
     semantics  and  usage.   arg  is  used to represent the
     flags argument to msync.  It is constructed from an  OR
     of the following values:
               MS_SYNC         Synchronized write
               MS_ASYNC        Return immediately
               MS_INVALIDATE   Invalidate mappings

MS_ASYNC returns after all I/O operations are scheduled. MS_SYNC does not return until all I/O operations are complete. Specify exactly one of MS_ASYNC or MS_SYNC. MS_INVALIDATE invalidates all cached copies of data from memory, requiring them to be re-obtained from the object's permanent storage location upon the next reference.

MC_UNLOCK

Unlock the pages in the range. This function is used to support munlock. See munlock(3) for semantics and usage. arg is ignored.

MC_UNLOCKAS

Remove address space memory lock, and locks on all current mappings. This function is used to support munlockall(3). addr and len must have the value 0. arg is ignored.

RETURN VALUE

mctl returns 0 on success, -1 on failure.

ERRORS

mctl fails if:

EAGAIN Some or all of the memory identified by the operation could not be locked due to insufficient system resources.

EBUSY MS_INVALIDATE was specified and one or more of the pages is locked in memory.

EINVAL addr is not a multiple of the page size as returned by getpagesize.

EINVAL addr and/or len do not have the value 0 when MC_LOCKAS or MC_UNLOCKAS are specified.

EINVAL arg is not valid for the function specified.

EIO An I/O error occurred while reading from or writing to the file system.

ENOMEM Addresses in the range [addr, addr + len) are invalid for the address space of a process, or specify one or more pages which are not mapped.