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>Can anyone tell me or point me to a source indicating the process/thread
>RAM limits for different Unixes?
>Alternatively, I'd be happy if anyone can tell me what their systems
>(max) limits are.
Traditionally, the limits of RAM per process are limited by two things:
how many bits in a pointer (assuming flat address spaces)
how much of the address space is used for other mappings
(traditionally, Unix systems map user and kernel space in one
address space to make user<->system switches and data copies
E.g., traditionally in SunOS/Solaris for SPARC the 32-bit kernel is mapped
above the end of the user's stack; the fact that kernels of larger systems
need a bigger address space lead to the strange fact that processes on
larger systems could use less memory. (3.75GB vs 3.5 or 3.25 GB).
However, with the advent of UltraSPARC cpus, a seperate kernel context
was added so swapping back and forth remained cheap but no longer took
away virtual memory from user processes. On UltraSPARC, 32 bit
processes can use 3.996GB of memory (4GB - 4MB) and not just 3.75GB.
Of course, systems have now progressed to the point where address
spaces are 64 bit and the typical limit is more in the order of
how much RAM you can stuff in a system (like 576GB in Sun's new F15K)
Expressed in this posting are my opinions. They are in no way related
to opinions held by my employer, Sun Microsystems.
Statements on Sun products included here are not gospel and may
be fiction rather than truth.