Fun with Futex

a year ago

Introduction to implementing locks in Linux, highlighting the need for OS assistance beyond user-land solutions.
Simple spin lock implementation in C using atomic operations for mutual exclusion.
Demonstration of a spin lock's inefficiency with high CPU usage when threads are waiting.
Introduction to futex (Fast Userspace Mutex) as a solution to reduce CPU consumption by putting waiting threads to sleep.
Explanation of futex operations: FUTEX_WAIT and FUTEX_WAKE, and their role in efficient lock implementation.
Implementation of a mutex using futex, detailing the structure and wrapper functions around the syscall.
Comparison between spin locks and futex-based locks, showing futex's advantage in scenarios with high contention.
Optimization of futex lock to avoid unnecessary syscalls by distinguishing between lock states (available, locked, locked with waiters).
Performance benchmarks comparing spin locks and optimized futex locks in different scenarios.
Discussion on potential improvements and further exploration topics like hybrid locks, fairness, and memory ordering.
List of references for further reading on futexes, locks, and concurrency in Linux.

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