HP-UX 11i June 2001 Release Notes

Process, Threads, Memory, and Kernel Parameters
Memory Windows
Chapter 8168
Memory Windows
Running without memory windows, HP-UX has limitations for shared
resources on 32-bit applications. All applications in the system are
limited to a total of 1.75GB of shared memory, 2.75GB if compiled as
SHMEM_MAGIC. In a system with 16GB of physical memory, only 1.75 can
be used for shared resources.
To address this limitation, a functional change has been made to allow
32-bit processes tocreate unique memorywindows for sharedobjects like
shared memory.
The memory window for default executables is 1GB.
This allows cooperating applications to create 1GB of shared resources
without exhausting the system-wide resource. Part of the virtual address
space remains globally visible to all processes, so that shared libraries
are accessible no matter what memory window they are in.
Summary of Changes
The following customer-visible changes have been made for memory
windows:
• New kernel tunable, max_mem_window, to configure the number of
memory windows a system can have.
• New set of commands and files (setmemwindow, getmemwindow,
/etc/services.window) to start applications in different memory
windows.
• Manpages for the new functionality have been created; they are
getmemwindow (1M), setmemwindow (1M), and services.window (4).
See the Memory Windows in HP-UX 11.0 White Paper on
http://docs.hp.com for details.
Compatibility Issues
Incorrect use of memory windows can lead to application failure.
Memory windows can be applied to any application but that does not
mean the application is able to run in memory windows. Some interfaces
may break when used under memory windows. HP does not consider this