C volatile variables and Cache Memory

Question

Cache is controlled by cache hardware transparently to processor, so if we use volatile variables in C program, how is it guaranteed that my program reads data each time fro

Answer 1

My suggestion is to mark the page as non-cached by the virtual memory manager.
In Windows, this is done through setting PAGE_NOCACHE when calling VirtualProtect.

For a somewhat different purpose, the SSE 2 instructions have the _mm_stream_xyz instructions to prevent cache pollution, although I don't think they apply to your case here.

In either case, there is no portable way of doing what you want in C; you have to use OS functionality.