How to use more than 3 GB in a process on a 32-bit Linux application with PAE support?

Question

PAE ( Physical Address Extension ) was introduced in the CPU back in 1994. This allows a 32-bit processor to access 64 GB of memory instead of 4 GB. Linux kernels offer support for this, starting with 2.3.23. Suppose I download one of these kernels and want to write a C application that will have access to more than 3 GB of memory (why 3 GB? See This ).

How do I access more than 3 GB of memory? Of course, I could refuse several processes; everyone will get access to 3 GB and will be able to communicate with each other. But this is not a realistic solution for most use cases. What other options are available?

Obviously, the best solution in most cases would be to simply boot in 64-bit mode, but my question is how to use physical memory above 4 GB in an application running on a 32-bit panel with support for the PAE kernel.

Answer 1

You don’t, directly - while you are working on a 32-bit basis, each process will obey the branching of the VM in which the kernel was built (2 GB, 3 GB or if you have a fixed kernel with a 4 GB / 4 GB connector, 4 GB).

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Answer 2

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Answer 3

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Answer 4

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Answer 5

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Answer 6

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You don’t have to do anything special. Only the kernel needs to access physical memory, and with PAE, it knows how to access physical memory above 4 GB. The application will use memory above 4 GB automatically and without problems.