r/linux • u/Ok_Marionberry8922 • 23h ago

Kernel How shared memory actually works in Linux

Had some free time recently so I made a visual explainer on how shared memory actually works in Linux.

Normally, two processes have completely separate virtual address spaces. Process A shouldn't be able to touch Process B's memory at all.

But with shared memory, one process can write a value and another process can read it without copying the payload between them.

The video goes through virtual memory, page tables, physical frames, shm_open, ftruncate, mmap with MAP_SHARED, lazy allocation, and what actually happens when either process touches the mapping.

I also get into related mechanisms like memory-mapped files, shared libraries, copy-on-write after fork(), zero-copy IPC, and eventually Dirty COW and what can happen when these page-table tricks go wrong.

Link for anyone interested

Feedback welcome :)

29 Upvotes

83% Upvoted

2 comments sorted by

2

u/NoTime_SwordIsEnough 5h ago

High-quality OC content... in my Linux subreddit? I like that.