Kevin Frie, the lead developer for core bits of the CLR just posted some information about the changes in .NET CLR 3.5 SP1. Heres an excerpt:
NGen infrastructure rewrite: the new infrastructure uses less memory, produces less fragmented NGen images with much better locality, and does so in dramatically less time. What this means to you: Installing or servicing an NGen image is much faster, and cold startup time of your NGen’ed code is better.
Framework Startup Performance Improvements: The framework is now better optimized for startup. We’ve tweaked the framework to consider more scenarios for startup, and now layout both code & data in the framework’s NGen images more optimally. What this means to you: Even your JIT code starts faster!
Better OS citizenship: We’ve modified NGen to produce images that are ASLR capable, in an effort to decrease potential security attack surface area. We’ve also started generating stacks that are always walkable using EBP-chaining for x86. What this means to you: Stack traces are more consistent, and NGen images aren’t as easily used to attack the system.
Better 32-bit code quality: The x86 JIT has dramatically improved inlining heuristics that result in generally better code quality, and, in particular, much lower “cost of abstraction”. If you want to author a data type that only manipulates a single integer, you can wrap the thing in a struct, and expect similar performance to code that explicitly uses an integer. There have also been some improvements to the ‘assertion propagation’ portion of the JIT, which means better null/range check elimination, as well as better constant propagation, and slight better ‘smarts’ in the JIT optimizer, overall. What this means to you: Your managed code should run slightly faster (and sometimes dramatically faster!). Note to 64 bit junkies: We’re working on getting x64 there, too. The work just wasn’t quite there in time.
Whats interesting to note is that the CLR Optimisations for inlining will finally be coming to the 64bit CLR, just hope that it comes sometime sooner rather than later.
In the meantime, grab the .NET Framework 3.5 SP1.