A GEM-ified TTM Manager For Radeon
Written by Michael Larabel in X.Org on 26 August 2008 at 08:15 AM EDT. 19 Comments
Back in May when X.Org developers were voicing concerns about Tungsten's TTM as being the kernel memory manager used for graphics drivers, Keith Packard had unveiled the work Intel had been doing for an alternate kernel memory manager. This memory manager they call GEM, or the Graphics Execution Manager, is a competing solution but it has some advantages such as being simpler to develop drivers around (A Technical Explanation of Intel's GEM). Intel then continued in throwing out their TTM code and merging GEM to master.

This unexpected introduction of GEM has caused the other driver developers to rethink their memory management situation and it has also generated some additional headaches within the X.Org community. For instance, a new X acceleration architecture has been introduced (albeit based off the EXA API) but with hooks for GEM. In addition, the forthcoming release of X Server 1.5 / X.Org 7.4 has lost DRI2 support since it depended upon the TTM interface.

Red Hat's David Airlie, who mostly works on the xf86-video-ati driver, has a brief update on some of the work he has been doing with GEM. In the DRI development mailing list, Airlie shares that he has removed all the TTM interfaces and ioctls from the kernel API, a DRM hardware lock file, object zeroing for the video memory, and has built a Radeon GEM interface that resides on top of the TTM internals. Some developers have voiced concerns about GEM being designed with just Intel in mind, but now David has an interface that's compliant with the GEM, but at it's heart is still TTM. This work can be found in his modesetting-gem git branch.
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Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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