What is the benefit of using RWMutex instead of Mutex?

Question

I am not sure when to use RWMutex and when to use Mutex.

Do you save resources if you use RWMutex instead of Mutex if you do more reads then writes?

I see some people use Mutex all the time no matter what they do, and some use RWMutex and run these methods:

func (rw *RWMutex) Lock() func (rw *RWMutex) Unlock() func (rw *RWMutex) RLock() func (rw *RWMutex) RUnlock() 

instead of just:

func (m *Mutex) Lock() func (m *Mutex) Unlock() 

If you save resources, is it that much of a difference that you should use RWMutex if you do more reads then writes?

Answer 1

From the docs (emphasize mine):

A RWMutex is a reader/writer mutual exclusion lock. The lock can be held by an arbitrary number of readers or a single writer. The zero value for a RWMutex is an unlocked mutex.

In other words, readers don't have to wait for each other. They only have to wait for writers holding the lock.

A sync.RWMutex is thus preferable for data that is mostly read, and the resource that is saved compared to a sync.Mutex is time.