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System Calls memcntl(2)
NAME
memcntl - memory management control
SYNOPSIS
#include <sys/types.h>
#include <sys/mman.h>
int memcntl(caddr_t addr, size_t len, int cmd, caddr_t arg,
int attr, int mask);
DESCRIPTION
The memcntl() function allows the calling process to apply a
variety of control operations over the address space identi-
fied by the mappings established for the address range
[addr, addr + len).
The addr argument must be a multiple of the pagesize as
returned by sysconf(3C). The scope of the control operations
can be further defined with additional selection criteria
(in the form of attributes) according to the bit pattern
contained in attr.
The following attributes specify page mapping selection cri-
teria:
SHARED Page is mapped shared.
PRIVATE Page is mapped private.
The following attributes specify page protection selection
criteria. The selection criteria are constructed by a bit-
wise OR operation on the attribute bits and must match
exactly.
PROT_READ Page can be read.
PROT_WRITE Page can be written.
PROT_EXEC Page can be executed.
The following criteria may also be specified:
SunOS 5.10 Last change: 1 Feb 2003 1
System Calls memcntl(2)
PROC_TEXT Process text.
PROC_DATA Process data.
The PROC_TEXT attribute specifies all privately mapped seg-
ments with read and execute permission, and the PROC_DATA
attribute specifies all privately mapped segments with write
permission.
Selection criteria can be used to describe various abstract
memory objects within the address space on which to operate.
If an operation shall not be constrained by the selection
criteria, attr must have the value 0.
The operation to be performed is identified by the argument
cmd. The symbolic names for the operations are defined in
<sys/mman.h> as follows:
MC_LOCK Lock in memory all pages in the range with
attributes attr. A given page may be locked
multiple times through different mappings;
however, within a given mapping, page locks
do not nest. Multiple lock operations on the
same address in the same process will all be
removed with a single unlock operation. A
page locked in one process and mapped in
another (or visible through a different map-
ping in the locking process) is locked in
memory as long as the locking process does
neither an implicit nor explicit unlock
operation. If a locked mapping is removed,
or a page is deleted through file removal or
truncation, an unlock operation is impli-
citly performed. If a writable MAP_PRIVATE
page in the address range is changed, the
lock will be transferred to the private
page.
The arg argument is not used, but must be 0
to ensure compatibility with potential
future enhancements.
MC_LOCKAS Lock in memory all pages mapped by the
address space with attributes attr. The addr
and len arguments are not used, but must be
NULL and 0 respectively, to ensure
SunOS 5.10 Last change: 1 Feb 2003 2
System Calls memcntl(2)
compatibility with potential future enhance-
ments. The arg argument is a bit pattern
built from the flags:
MCL_CURRENT Lock current mappings.
MCL_FUTURE Lock future mappings.
The value of arg determines whether the
pages to be locked are those currently
mapped by the address space, those that will
be mapped in the future, or both. If
MCL_FUTURE is specified, then all mappings
subsequently added to the address space will
be locked, provided sufficient memory is
available.
MC_SYNC Write to their backing storage locations all
modified pages in the range with attributes
attr. Optionally, invalidate cache copies.
The backing storage for a modified
MAP_SHARED mapping is the file the page is
mapped to; the backing storage for a modi-
fied MAP_PRIVATE mapping is its swap area.
The arg argument is a bit pattern built from
the flags used to control the behavior of
the operation:
MS_ASYNC Perform asynchronous writes.
MS_SYNC Perform synchronous writes.
MS_INVALIDATE Invalidate mappings.
MS_ASYNC Return immediately once all write
operations are scheduled; with MS_SYNC the
function will not return until all write
operations are completed.
SunOS 5.10 Last change: 1 Feb 2003 3
System Calls memcntl(2)
MS_INVALIDATE Invalidate all cached copies
of data in memory, so that further refer-
ences to the pages will be obtained by the
system from their backing storage locations.
This operation should be used by applica-
tions that require a memory object to be in
a known state.
MC_UNLOCK Unlock all pages in the range with attri-
butes attr. The arg argument is not used,
but must be 0 to ensure compatibility with
potential future enhancements.
MC_UNLOCKAS Remove address space memory locks and locks
on all pages in the address space with
attributes attr. The addr, len, and arg
arguments are not used, but must be NULL, 0
and 0, respectively, to ensure compatibility
with potential future enhancements.
MC_HAT_ADVISE Advise system how a region of user-mapped
memory will be accessed. The arg argument is
interpreted as a "struct memcntl_mha *". The
following members are defined in a struct
memcntl_mha:
uint_t mha_cmd;
uint_t mha_flags;
size_t mha_pagesize;
The accepted values for mha_cmd are:
MHA_MAPSIZE_VA
MHA_MAPSIZE_STACK
MHA_MAPSIZE_BSSBRK
The mha_flags member is reserved for future
use and must always be set to 0. The
mha_pagesize member must be a valid size as
obtained from getpagesizes(3C) or the con-
stant value 0 to allow the system to choose
an appropriate hardware address translation
mapping size.
MHA_MAPSIZE_VA sets the preferred hardware
SunOS 5.10 Last change: 1 Feb 2003 4
System Calls memcntl(2)
address translation mapping size of the
region of memory from addr to addr + len.
Both addr and len must be aligned to an
mha_pagesize boundary. The entire virtual
address region from addr to addr + len must
not have any holes. Permissions within each
mha_pagesize-aligned portion of the region
must be consistent. When a size of 0 is
specified, the system selects an appropriate
size based on the size and alignment of the
memory region, type of processor, and other
considerations.
MHA_MAPSIZE_STACK sets the preferred
hardware address translation mapping size of
the process main thread stack segment. The
addr and len arguments must be NULL and 0,
respectively.
MHA_MAPSIZE_BSSBRK sets the preferred
hardware address translation mapping size of
the process heap. The addr and len arguments
must be NULL and 0, respectively. See the
NOTES section of the ppgsz(1) manual page
for additional information on process heap
alignment.
The attr argument must be 0 for all
MC_HAT_ADVISE operations.
The mask argument must be 0; it is reserved for future use.
Locks established with the lock operations are not inherited
by a child process after fork(2). The memcntl() function
fails if it attempts to lock more memory than a system-
specific limit.
Due to the potential impact on system resources, the opera-
tions MC_LOCKAS, MC_LOCK, MC_UNLOCKAS, and MC_UNLOCK are
restricted to privileged processes.
USAGE
The memcntl() function subsumes the operations of plock(3C)
and mctl(3UCB).
MC_HAT_ADVISE is intended to improve performance of applica-
tions that use large amounts of memory on processors that
support multiple hardware address translation mapping sizes;
however, it should be used with care. Not all processors
support all sizes with equal efficiency. Use of larger sizes
SunOS 5.10 Last change: 1 Feb 2003 5
System Calls memcntl(2)
may also introduce extra overhead that could reduce perfor-
mance or available memory. Using large sizes for one appli-
cation may reduce available resources for other applications
and result in slower system wide performance.
RETURN VALUES
Upon successful completion, memcntl() returns 0; otherwise,
it returns -1 and sets errno to indicate an error.
ERRORS
The memcntl() function will fail if:
EAGAIN When the selection criteria match, some or
all of the memory identified by the opera-
tion could not be locked when MC_LOCK or
MC_LOCKAS was specified, some or all map-
pings in the address range [addr, addr +
len) are locked for I/O when MC_HAT_ADVISE
was specified, or the system has insuffi-
cient resources when MC_HAT_ADVISE was
specified.
EBUSY When the selection criteria match, some or
all of the addresses in the range [addr,
addr + len) are locked and MC_SYNC with the
MS_INVALIDATE option was specified.
EINVAL The addr argument specifies invalid selec-
tion criteria or is not a multiple of the
page size as returned by sysconf(3C); the
addr and/or len argument does not have the
value 0 when MC_LOCKAS or MC_UNLOCKAS is
specified; the arg argument is not valid for
the function specified; mha_pagesize or
mha_cmd is invalid; or MC_HAT_ADVISE is
specified and not all pages in the specified
region have the same access permissions
within the given size boundaries.
ENOMEM When the selection criteria match, some or
all of the 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.
SunOS 5.10 Last change: 1 Feb 2003 6
System Calls memcntl(2)
EPERM The {PRIV_PROC_LOCK_MEMORY} privilege is not
asserted in the effective set of the calling
process and MC_LOCK, MC_LOCKAS, MC_UNLOCK,
or MC_UNLOCKAS was specified.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
ppgsz(1), fork(2) mmap(2), mprotect(2), getpagesizes(3C),
mctl(3UCB), mlock(3C), mlockall(3C), msync(3C), plock(3C),
sysconf(3C), attributes(5), privileges(5)
SunOS 5.10 Last change: 1 Feb 2003 7
Man(1) output converted with
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This page was generated on Wed Sep 12 11:27:02 GMT 2007
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