How does a stack memory increase?

Question

Hello,

In a typical C program, the linux kernel provides 84K - ~100K of memory. How does the kernel allocate more memory for the stack when the process uses the given memory.

IMO when the process takes up all the memory of the stack and now uses the next contiguous memory, ideally it should page fault and then the kernel handles the page fault. Is it here that the kernel provides more memory to the stack for the given process, and which data structure in linux kernel identifies the size of the stack for the process??

Answer 1

The stack for a given process has a limited, fixed size. The reason you can't add more memory as you (theoretically) describe is because the stack must be contiguous, and it grows toward the heap. So, when the stack reaches the heap, no extension is possible.

The stack size for a userland program is not determined by the kernel. The kernel stack size is a configuration option for the kernel (usually 4k or 8k).

Edit: if you already know this, and were merely talking about the allocation of physical pages for a process, then you have the procedure down already. But there's no need to keep track of the "stack size" like this: the virtual pages in the stack with no pagetable entries are just normal overcommitted virtual pages. Physical memory will be granted on their first access. But the kernel does not have to overcommit memory, and thus a stack will probably have complete physical realization when the executable is first loaded.