2.6.39-cleancache is a kernel.
Frontswap Still Not Ready For Linux 3.3 Kernel: While the Frontswap patches with Cleancache have been available for several Linux kernel release cycles, the Frontswap support still hasn't been merged. Another Oracle developer is now taking over maintenance of Cleancache and getting Frontswap finally ready for merging, but it's too late for the Linux 3.3 kernel...
CleanCache Merged Into The Linux Kernel: While the first Phoronix benchmarks of EXT4, Btrfs, and XFS on the Linux 2.6.39 kernel were just published this morning, an interesting change was just made for the next Linux kernel that will affect many of the file-systems living within the kernel. For what will be the Linux 2.6.40 kernel, or rather the Linux 3.0 kernel is the finally-merged support for CleanCache...