ATI Open vs. Closed-Source AIGLX Performance
For those that may have missed it, the ATI/AMD fglrx 8.42 display driver that was released last month had introduced AIGLX support. The open-source "Radeon" driver for ATI graphics cards going up to the R400 generation has supported AIGLX for quite some time, but the ATI binary display driver hadn't until last month. However, one of the complaints about the fglrx implementation of AIGLX is that in the 8.42.3 driver, some are encountering slow performance in Compiz / Compiz Fusion. We have taken an ATI Radeon X800XL 256MB PCI-E graphics card, which is supported by both the Radeon and fglrx drivers, and have compared their Compiz performance in a few different scenarios.
Compiz 0.6.0 was used with Ubuntu 7.10 "Gutsy Gibbon" and the Linux 2.6.22 kernel with X server 1.3. The hardware included a PCI Express x16 based ATI Radeon X800XL with 256MB of video memory, an Intel Pentium D 820 (2.80GHz dual-core) processor, 2GB of DDR3-1333 memory, and an ASUS P5E3 Deluxe (Intel X38 Chipset) motherboard. While these tests are not scientific, we had used the Compiz Benchmark plug-in to measure the frame-rate when different Compiz effects were occurring on the desktop. These test scenarios had included the fire effect, water effect, window hovering, and then just idling within the GNOME 2.20 desktop. Testing was done with the stock "Radeon" driver that ships with Ubuntu 7.10 and with the fglrx 8.42.3 binary driver.
While sitting within the GNOME desktop and just having one Nautilus window open, using the Radeon driver had a reported 111 frames per second according to Compiz Benchmark while the fglrx driver performance was nearly double that with 194 frames per second.
Though the Compiz fire effect isn't practical, it does stress the system. The Radeon driver had an average frame-rate of 58 FPS while the binary driver had dipped down to 48 FPS.
When hovering over a Mozilla Firefox 2.0 window on the GNOME panel, the open-source Radeon driver was at 98 FPS and fglrx at 182 FPS.
Another not too practical but system-stressful effect is the water display. While the desktop was raining, the Radeon frame-rate was at 36 FPS and the fglrx at 66 FPS.
While these benchmarks are not scientific and far from covering all of the different use cases for Compiz, to no real surprise the fglrx binary display driver does offer better performance than the reverse-engineered R300/400 support in the open-source Radeon driver. The only test where the fglrx driver had performed worse than the open-source alternative was when using the fire effect. It is also important to keep in mind that the CPU also comes into play when using Compiz / Compiz Fusion and that will also impact your performance. Certainly, AMD engineers will be working towards enhancing its AIGLX implementation in their fglrx driver along with more features in future driver releases.
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