How does Ruby handle thread scheduling and what role does the operating system play?

Ruby threads are mapped to native OS threads, but scheduling is influenced by Ruby’s GVL and the OS scheduler.

In CRuby, threads are OS-level threads, but execution is constrained by the Global VM Lock (GVL), meaning only one thread executes Ruby code at a time. The OS scheduler still handles thread switching, but Ruby periodically releases the GVL during blocking operations like I/O. This allows concurrency but not true parallel execution for CPU-bound Ruby code.