The Radeon DRM driver finally has page-flipping support with this updated DRM to be found in the Linux 2.6.38 kernel (along with other features like PCI-E 2.0 and Radeon HD 6000 series / Fusion support), which should offer a nice performance boost for the open-source Radeon driver after the Nouveau and Intel open-source drivers have had this support for a few months already.
However, to take advantage of this page-flipping support you also need an updated xf86-video-ati driver. While the page-flipping support was living out of the mainline kernel the DDX driver had to be checked out from the kms-pflip branch of the driver, but now it's been merged into master. With this Git commit the support has landed.
This commit adds an EnablePageFlip xorg.conf option for enabling the DRI2 page-flipping support, but by default it's enabled. There is also the SwapbuffersWait xorg.conf option for avoiding tearing on the screen by providing scan-line synchronization, but it comes at the cost of reduced frame-rates. Last but not least, this commit also enables tiling for the R600 ASICs and later. Up to this point tiling has been only enabled for the R500 GPUs and earlier in the form of macro tiling, but now the R600 and newer ASICs have support for micro tiling enabled by default.
These xf86-video-ati improvements will be found in version 6.14.0 of the driver, which should be released around the time that the Linux 2.6.38 kernel surfaces.