For Java …
Highlight for today:
-XX:+UseBiasedLocking – An object is ”biased” toward the thread which first acquires its monitor via a monitorenter bytecode or synchronized method invocation; subsequent monitor-related operations performed by that thread are relatively much faster on multiprocessor machines. Some applications with significant amounts of uncontended synchronization may attain speedups with this flag enabled (don’t use by default, could easily slow down the multithreaded apps)
Some performance analysis results:
1.5.0_06 performance annomaly
NOTE: It was mentioned that this flag is by default on in JDK 6.0 (but not in JDK .50).