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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 criteria:

   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:

   PROC_TEXT
      Process text.

   PROC_DATA
      Process data.

System Calls                      memcntl(2)

   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 opera-
      tions 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 visi-
      ble through a different mapping in the locking pro-
      cess) is locked in memory as long as the locking pro-
      cess 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 implicitly performed. If a writ-
      able 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 compatibility with potential future enhance-
      ments. The arg argument is a bit pattern built from
      the flags:

      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.


      MCL_CURRENT
         Lock current mappings.

      MCL_FUTURE
         Lock future mappings.
   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  modified
      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.

      MS_INVALIDATE Invalidate all cached copies of data in
      memory, so that further references 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 attributes 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:

System Calls                      memcntl(2)
      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 constant value 0 to allow the system to choose an
      appropriate hardware address translation mapping size.

      MHA_MAPSIZE_VA sets the preferred hardware 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 con-
      siderations.

      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, all opera-
   tions except MC_SYNC are restricted to processes with
   superuser effective user ID.

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
   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 operation could not be locked
      when MC_LOCK or MC_LOCKAS was specified, some or all
      mappings in the address range [addr, addr + len) are
      locked for I/O when MC_HAT_ADVISE was specified, or
      the  system  has  insufficient  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 speci-
      fied.



   EINVAL
      The addr argument specifies invalid selection 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 func-
      tion 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.

   EPERM The process's effective user ID is not superuser 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)
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