If you notice your Mac performing a little smoother since installing OS X Mavericks, it could be due to advances in memory management and the return of memory compression.
Memory Pressure and How Your Mac Uses Memory
With the release of OS X Mavericks, Apple changed the way the Mac managed memory. The addition of memory compression lets your Mac do more with less memory while maintaining or improving performance. In previous versions of OS X, memory usage was built around a standard memory management system. Apps would request an allocation of RAM, the system would honor the request, and the apps would give the RAM back when they no longer needed it.
The operating system did most of the work of keeping track of how much RAM was available and who was using it. The operating system also figured out what to do if the necessary amount of RAM was not available, which could have a negative effect on the Mac's performance as the system attempted to take advantage of virtual RAM by swapping space on an SSD or hard drive.
Compressed memory isn't something new or exclusive to Apple. Computer systems have used various forms of memory compression for a long time. If you used Macs in the mid-'80s and early '90s, you may remember products like Connectix's RAM Doubler, which compressed data stored in RAM, effectively increasing the amount of free RAM available to the Mac.
