PolarQuant is doing most of the compression, but the second step cleans up the rough spots. Google proposes smoothing that out with a technique called Quantized Johnson-Lindenstrauss (QJL).
Both work with Linux's existing swapping mechanism. Swapping (called paging in Windows) is a way for the kernel to handle running low on available RAM. It chooses pages of memory that aren't in use right now and copies them to disk, then those blocks can be marked as free and reused for something else.
The headline runtime feature in this preview is Runtime Async, described as a major change to how asynchronous methods work in .NET. According to the release notes, since C# 5 introduced async/await, the compiler has been solely responsible for rewriting async methods into state machine structs that track progress across suspension points. With Runtime Async, the runtime itself now understands async methods as a first-class concept and takes over responsibility for suspending and resuming methods.
