Linux Response time

I try to evaluate context-switch response time.

I use 2 threads and 2 mutexes.

Thread A waits for mutex A and releases mutex B, thread B releases mutex A and waits for mutex B.

It gives me the following (in microseconds)

27 µs for µC/OS-II on NIOSII 'fast' at 50 MHz.

430 µs for Linux on NIOSII (same configuration).

[As a reference, 29 µs for VxWorks on a 133MHz AMD5x86]

Is Linux really so bad (16 times) ?

Is there something faster than pthread_() ?