Let say the system starts two processes A and B. How the virtual address of process A and process B was allocated?


Thank you.

This looks like a homework question.

If so, please show us some of the work you've done to answer it before you turned to LQ for assistance.

Oh,sorry! It's not a homework question,but it may seem to be.
I am read the book-<the design of the unix operating system>,and now I have reached the chapter6.
In chapter6 the author says the virtual address space of a process into logical regions.But the author didn't give much detail about it.
So I just wonder how the system decides what virtual address space to give the new process when starts it.

The virtual address space is what the linker (ld) compiled into the executable.
The physical addresses (and it doesn't have to be a single space) is where the kernel can find room in the current RAM usage to load one or more pages OF the executable.
But that's invisible to the application itself.
PS: even malloc's will return virtual address values, that is, addresses that the program can use TO access the newly allocated memory. Again: the program doesn't need to know where in RAM this memory has been found.
The physical address of a page may even vary during the execution of the program.

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Thanks for straightening me out. Clearly, you are digging deep into that material.

I found a page at kernel.org that might be helpful. I can't say for sure, because it made my brain hurt.

https://www.kernel.org/doc/gorman/ht...rstand007.html

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