Good article Alex.

A spinlock will be faster than a mutex.
A spinlock is a mechanism that gives a thread the ability to not get
pre-empted (or blocked) by the kernel.
The side effect to this is that a thread that is waiting on a spinlock is more responsive, at the cost of cpu (since it will be spinning).
Since the thread is more responsive, it will execute it’s instructions in less wall clock time.

A point to be noted is that a spinlock will not spin infinitely (the spin count is not documented), so in a worst case scenario a spinlock downgrades to a mutex.
Replacing all the mutex locks with spinlocks will only improve performance -
not degrade it.

Somebody wrongly noted that a spinlock will lead to “priority inversion” scenarios. This is not true.

The argument that spinlocks are useless on single processor machines, though
correct, should not be taken seriously since here are not many single
processor machines around anymore.

There are numerous cases where spinlocks are applicable.
A simple example is a message processor app.
eg: Thread(T1) reads from a socket and write to a queue(Q), Thread(T2) reads from the Q and does some processing. In this case the lock on the Q is very short lived and the threads T1, T2 have to be very responsive.

enjoy

$ g++ -o threadTest_spin -DUSE_SPINLOCK -lpthread threadTest.cpp
$ g++ -o threadTest_mutex -lpthread threadTest.cpp
$ ./threadTest_mutex
Thread test using mutex.
Consumer TID 6838
Consumer TID 6837
Result – 2.638293
$ ./threadTest_spin
Thread test using spin lock.
Consumer TID 6847
Consumer TID 6848
Result – 1.926722

$ g++ -o threadTest_spin -DUSE_SPINLOCK -O3 -lpthread threadTest.cpp
$ g++ -o threadTest_mutex -O3 -lpthread threadTest.cpp
$ ./threadTest_mutex
Thread test using mutex.
Consumer TID 6821
Consumer TID 6822
Result – 1.589208
$ ./threadTest_spin
Thread test using spin lock.
Consumer TID 6824
Consumer TID 6825
Result – 1.667864

2.6.38-ARCH x86_64 Intel(R) Core(TM)2 CPU 4400 @ 2.00GHz, g++ 4.6.0 20110513