Operating Systems: Three Easy Pieces

Why This Book

OSTEP is free, well-written, and covers the three pillars of OS design with unusual clarity: virtualization (CPU + memory), concurrency, and persistence (storage). The conversational style makes dense material approachable without dumbing it down.

Structure

The book is organized around its title — three “easy pieces”:

• Virtualization — processes, scheduling, address spaces, paging, swapping. The best introduction to virtual memory I’ve found, with the right level of x86 specificity.
• Concurrency — locks, condition variables, semaphores, deadlock. Covers both the theory and the gotchas.
• Persistence — I/O devices, disks, RAID, filesystems, journaling, log-structured filesystems. The filesystem section is exceptional.

What I Keep Coming Back To

The scheduling chapters (CFS walkthrough), the address space chapters (segmentation → paging transition), and the filesystem chapters (ext-style inodes, journaling correctness) are the sections I re-read most.

Caveats

• Lighter on Linux-specific internals than TLPI or CSAPP
• The concurrency material is solid but doesn’t go deep on memory ordering / atomics
• Some homework problems assume simulators from the course website

Verdict

Free, readable, and comprehensive. Start here if you’re new to OS internals. Read it alongside CSAPP for the best coverage.