[gclist] synchronization cost (was: Garbage collection and XML)

[Ji-Yong D. Chung]

    And I forgot to mention that EnterCriticalSection takes (I have read)
about 6 CPU cycles in optimal case.

    I have seen implementations of non-reentrant spin locks
that  take a 5 cycles per lock (implemented using
LOCK and XCHG and MOV.  LOCK takes 1 CPU cycle, XCHG takes
3 CPU cycles and MOV takes 1 cycle).