We Can Automatically Find Functional Regressions Too

Last October we reported on new capabilities within the Phoronix Test Suite that allowed performance regressions to be located within any code-base by leveraging our open-source testing framework with the git-bisect command to automatically traverse a tree in a binary manner until the Phoronix Test Suite spots the regression-causing commit. As an example we tracked down a regression in the mainline Linux kernel with the EXT4 file-system without any manual intervention. Now not only can we automatically track down any performance regressions, but the Phoronix Test Suite can also help you spot any functional regressions.

In testing out the very latest xf86-video-intel DDX driver code to look at how the UXA performance enhancements are working in the forthcoming 2.12 Intel X.Org driver release, I had installed the latest driver Git code (along with the updated libdrm) on the Samsung NC10 netbook with the Intel 945 integrated graphics. However, the X.Org Server failed to properly start and wouldn't get past displaying the cursor.

This led to the creation of a simple test profile that just used a pass-fail result type and updating the Phoronix Test Suite's auto-bisecting module to supporting these non-numeric results. Next I let the Phoronix Test Suite bisect the xf86-video-intel driver between the previous 2.11.0 release that worked fine on the NC10 and then the latest Git master code. A little while later, the commit introducing the problem was found.

Analyzing the problematic commit, a workaround the Intel driver Git master was devised. The new Intel 2D performance testing was then able to move forward and those results will be published in the next day or two. This functional regression auto-bisecting support will likely be pushed into Phoronix Test Suite 2.8 so others can benefit from these capabilities.

For anyone experiencing a similar problem with the Intel driver Git code, see this FreeDesktop.org bug report that was created once the Phoronix Test Suite tracked down the problem.