Subj : performance of single mutex versus Read/write mutex: any numbers? discuss
To   : comp.programming.threads
From : Mike Winter
Date : Wed Oct 05 2005 09:47 pm

If I have a small critical section to access an element of a structure 
(queue) and most accesses are reads and once in a blue moon a write (PI 
seconds is a nano-century!) occurs where the primary element is superceded, 
but only completely superceded when its reference count is 0(no more 
readers), I think a single mutex may be overkill. I would think that a 
single mutex would be less performant than say a more complex structure like 
say a read-write mutex. Then I think about what it takes to manage a 
ReadWriteMutex (mutex + reader-count + writing).

Consider

struct ReadWriteMutex {
      Mutex    mWriterMutex;    // gets grabbed rarely
      AtomicCounter mReaderCount;  // gets incremented/decremented securely 
and fast
      ReaderMutex  mReaderMutex;   // only blocks if mWriterMutex is locked
};

Thats the context/concept.

Heres the question: Are there any numbers /papers in the ether that can 
point to how the ReaderWriterMutex will compare to the ordinary Mutex? Links 
welcomed

MW

.