Memory: paging, virtual memory and page faults

Address translation with real hex numbers, and FIFO versus LRU counted out on a reference string.

13 min read · Lesson 5 of 6 · Pro

Every address your program sees is fake

Run two copies of the same program at once and both may print the address 0x55a4c8e012a0 for the same variable. They are not sharing memory. Each sees its own virtual address space, and the hardware maps those virtual addresses to different physical RAM.

Virtual memory buys three things. Isolation — your process has no way to name another process's physical memory. Simplicity — every program is compiled assuming it starts at the same address. More memory than you have — unused pages can sit on disk, so a 6 GB working set runs on a 4 GB machine, slowly.

Pages, frames and translation

The rest of this lesson is Pro

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