I have been looking for information on the web regarding use of the Java Concurrent Mark Sweep GC for Linux and Mac or for different versions of Java. I'm specifically interested in the latest versions of Oracle Java 1.6 and 1.7.
I'll assume that it runs because I haven't found anything to the contrary, but are there any noticeable differences of the performance as compared to Windows, including on OpenJDK?
This depends on the JVM implementation. You did not specify the JVM vendor/distribution you are interested in. I am sure there are VMs out there where you can see a performance difference depending on the OS.
But, in general as long as only the GC algorithm is concerned, there will be no difference on any platform because the code implementing the GC algorithm is the same. The GC algorithm is accessing an API for low level system routines that implement the allocation/deallocation of the memory. The implementation of such API depends on OS.