PH32235: NEW FUNCTION ? Language Environment is enhanced to support 64bitmapping in mmap()

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• NEW FUNCTION
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * z/OS XL C/C++ users who want to exploit mmap() 64bit mapping *
  * support                                                      *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Analytics applications attributed to memory mapping very     *
  * large files have limited performance and scalability on      *
  * z/OS.                                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  

Problem conclusion

Temporary fix

Comments

• Publication updates:
  z/OS XL C/C++ > z/OS XL C/C++ Programming Guide >
  Coding: Advanced Topics > Using environment variables >
  Environment variables specific to the z/OS XL C/C++ library
  _EDC_AUTO_MAP64
  Setting _EDC_AUTO_MAP64 to YES causes __MAP_64 flag to be added
  for all mmap() calls in
  AMODE 64.
  Value
  Description
  YES
  Add __MAP_64 flag automatically for mmap() calls in AMODE 64.
  <other>
  Do nothing; this is the default.
  
  z/OS XL C/C++ > z/OS XL C/C++ Runtime Library Reference >
  Library functions >
  mmap() ? Map pages of memory
  
  __MAP_64
  Map storage above the 2-gigabyte addressing range
  
  64bit mapping support: 64 bit mapping support will be specified
  by either using the __MAP_64 in the flags argument, or by
  providing an addr above 64G, or providing a len greater than 2G.
  - If the first mapping of a file uses the 64 bit support, then
  all subsequent mappings of the file must also use 64 bit support
  until such time as there are no more mappings onto that file. If
  an attempt is made to map the file without using 64 bit support,
  an EINVAL error will be returned.
  - If the first mapping of a file uses the 31 bit support, then
  all subsequent mappings of the file must also use 31 bit support
  until such time as there are no more mappings onto that file. If
  an attempt is made to map the file without using 31 bit support,
  an EINVAL error will be returned.
  
  Usage notes
  1. The mmap() function does not support shared memory objects or
  typed memory objects.
  2. If __MAP_64 is specified then the addr argument must either
  be 0 or a value greater than 64G or EINVAL will be returned.
  3. If both __MAP_64 and MAP_FIXED are specified, then the first
  fullword of the addr argument must be nonzero or EINVAL will be
  returned.
  4. For non-MAP_FIXED requests, if the addr specifies an address
  above 64G, the system attempts to create a mapping at the
  address specified by addr and the address is truncated to the
  nearest megabyte boundary. If it is unsuccessful, it proceeds as
  if an addr value of zero were specified, but will attempt to
  create a mapping above 64G.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UI74844

Modules/Macros

• CELHXFR4 CELQINC  CELJGTNV EDC40358 CELHGTNV CELZGTNV CELQGTNV
  CELQXFR4 EDC4H04B EDC4009F
  

Fix information

• Fixed component name

  LE C LIB FOR Z/

• Fixed component ID

  568819805

Applicable component levels

• R7C0 PSY UI74844

     UP21/04/28 P F104

Fix is available

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