Peter Anvin and others have long been working towards Linux x32: a native 32-bit ABI for Intel/AMD 64-bit systems so that applications not needing 64-bit pointers can benefit from 64-bit performance while using the memory foot-print of a 32-bit ABI. The Linux x32 ABI support necessitates changes to GNU binutils, the Linux kernel, Glibc, and the compiler (GCC). On Sunday the set of 30 patches touching around 1,000 lines of code was sent off to the kernel mailing list by Anvin.
Benchmarks by the developers have shown that x32 can be about up to 32% faster than x86_64 in some CPU benchmarks. However, in some cases it can also be slightly slower than x86_64 and/or ia32.
Those not familiar with Linux x32 can learn more from the x32abi Google Site where there are some benchmarks, setup information for building the necessary components and/or using the Gentoo or Fedora versions, and other information on the x32 ABI. The slides from the x32 presentation that Anvin did at least year's Linux Plumbers Conference are also available.
The x32 kernel changes isn't a pull request that Peter sent in with his mailing list message, but rather an RFC (Request For Comments). Anvin acknowledges there are some controversial issues as well as areas of incompleteness, but he's currently looking for review on the changes. Right now the work is based upon the Linux 3.3-rc3 kernel.