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Monthly Archives: April 2012

A month in, and we’re starting to get some good feedback from people trying cairo-1.12. Unfortunately, it appears that we’ve exposed some bugs in a few drivers, though hopefully we will see driver updates to resolve those issues shortly. We also received a few bug reports against Cairo itself. The most bizarre perhaps was that LibreOffice failed to display the presentation slideshow. That turned out to be an inadvertent bug caught by better error detection – though since that affected the established API, we had to relax the checks somewhat. Along with a few other bug fixes, Cairo 1.12.2 was released.

In the last round of benchmarking I performed, some of you noticed that the glamor backend for the Intel driver was not included. It was left out for the simple reason that it was not able to complete the task. However with the first stable release of glamor-0.4, it is able to complete a benchmarking run. And so without further ado, let’s see how all the current drivers fare on a SandyBridge i5-2500 desktop with GT1 integrated graphics and a Radeon HD 5770 discrete GPU with cairo-1.12.2.

Performance of cairo-1.12.2 on i5-2500

This time the results are normalized to the performance with Xvfb. Any driver that performs a test faster is above the centre, any that were slower below. Again the general state of the drivers leave much to be desired, and despite the bold claims for glamor, in my testing it fails to improve upon UXA. Early days you might say.

I do have a SandyBridge desktop. This system is a bit special as it is the one in which I can run a discrete card in direct comparison to the ingrated processor graphics, i.e. run both GPUs simultaneously (but not yet co-operatively). In this system I put a Radeon HD5770 which at the time was a mid-range GPU offering good value for performance. So how does Cairo fare on this box? In particular are the DDX drivers any better than pixman, the backend for Cairo’s software rasteriser?

Cairo performance on a Radeon HD5770

Once again the white baseline in the centre represents the performance of the image backend, how fast we expect to be able to render the contents ourselves. Above that baseline, the driver is faster; below slower, laggy and power hungry. This is quite a busy graph as it compares the performance of the propietary fglrx driver and the open-source radeon driver along with the alternative acceleration methods for the integrated graphics. I’d recommend viewing at full size, but the gist of it is that in many cases the propietary driver lags behind the open-source effort. Neither are truly comparable to just using the CPU and only the open-source effort is ever faster. In contrast, we have the integrated processor graphics. Even this GT1 desktop system (only half the GPU capability of a GT2 system such as found on mobiles and on a few desktop chips) can outclass the CPU. When not limited by a poor driver, that is.

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