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Name

mctl - memory management control

Synopsis

/usr/ucb/cc [ flag ... ] file ... 


#include <sys/types.h>
#include <sys/mman.h>

int mctl( addr, len, function, arg)
caddr_t addr;
size_t len;
int function;
int 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(3C) 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(3C) for semantics and usage. addr and len are ignored. arg is an integer built from the flags:

MCL_CURRENT    Lock current mappingsMCL_FUTURE    Lock future mappingsMC_SYNC

Synchronize the pages in the range with their backing storage. Optionally invalidate cache copies. This function is used to support msync(). See msync(3C) 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 writeMS_ASYNC    Return immediatelyMS_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(). arg is ignored.
MC_UNLOCKAS
Remove address space memory lock, and locks on all current mappings. This function is used to support munlockall(). addr and len must have the value 0. arg is ignored.

Return Values

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.
EPERM
The process’s effective user ID is not super-user and one of MC_LOCK MC_LOCKAS , MC_UNLOCK , or MC_UNLOCKAS was specified.

See Also

mmap(2) , memcntl(2) , getpagesize(3C) , mlock(3C) , mlockall(3C) , msync(3C)

Notes

Use of these interfaces should be restricted to only applications written on BSD platforms. Use of these interfaces with any of the system libraries or in multi-thread applications is unsupported.

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