Lima Driver Has Some Speed Wins, But Will Not Be Mainlined

The Lima graphics driver for open-source ARM Mali GPU support on Linux has some performance advantages of ARM Holdings' binary blob, but there's no upstream interest in having the driver mainlined in Mesa.

Last week at XDC2013 there was the state of the open-source ARM GPU drivers. The Lima driver was covered during the presentation by Rob Clark, while in chatting with Luc Verhaegen a few days ago I managed to pick up a couple more details.

Luc expressed that the performance of his Lima driver is "consistently beating the binary" in the range of 6~10% better for GLMark2 and ES2_Gears tests within his Limare driver tests. He also says there's still better performance to be had because under X11 there is no job interleaving right now so he believes there's about 50% performance to be gained by better integration with the display engine and X.Org DDX driver.

Verhaegen believes in the end they should be able to achieve 60% better OpenGL ES performance over ARM's official Mali graphics driver for Linux. He also says he and the few developers involved in the project are also planning Wayland and Mir support. One of the issues that remains outstanding though is the Lima driver is dependent upon ARM's binary shader compiler and that at the moment they don't have a full open-source shader compiler for their driver.

While there's great ambitions for this driver, promising performance results, and Luc continues working on it a lot while being presently unemployed, he doesn't want to mainline the driver in Mesa. Luc has been writing Lima as a classic Mesa driver (not Gallium3D-based) as it's easier to connect into his current shader compiler approach, etc. However, when I asked if he has plans yet to push it into mainline Mesa Git, he said, "I do not want to mainline it...It is pretty nice to be able to build it externally...especially for small hardware like this with turn-around and testing times are very low."