MySQL 5.5 modifications improve performance on SMP
systems to increase scalability on multi-core systems. The
InnoDB locking and
MySQL 5.5 incorporates changes in
InnoDB that improve the performance
of RW-locks by using atomic CPU instructions (on platforms where
they are available), rather than less scalable mutexes. It is
also possible for
allocation to be disabled and replaced by the normal
malloc library, or by a different library
malloc such as
tcmalloc on Linux or
mtalloc on Solaris.
The reimplementation of RW-locks requires atomic instructions. A
shows whether the server was built with atomic instructions.