I'll never forget this post:
Gabe Newell himself wrote a lot of this post in front of me. From what I could tell, he seemed flabbergasted and annoyed that the team didn't immediately blog this info once we were solidly running faster in OpenGL vs. D3D. (Of course we should have blogged it ourselves! One of our missions as a team inside of Valve was to build a supportive community around our efforts.) From his perspective, it was big news that we were running faster on Linux vs. Windows. I personally suspect his social network didn't believe it was possible, and/or there was some deeper strategic business reason for blogging this info ASAP.
I stood behind Gabe and gave him all the data concerning GL vs. D3D performance while he typed the blog post in. I was (and still remain) extremely confident that our results were real. We conducted these tests as scientifically as we could, using two machines with the same hardware, configured in precisely the same way in the BIOS's, etc. NVidia and AMD were able to reproduce our results independently. Also, I could have easily made L4D2 on Linux GL run even faster vs. Windows, but we had other priorities like getting more Source1 games working, and helping Intel with their open source GL driver. From what I understand, Linux has some inherent advantages at the kernel level vs. Windows that impact driver performance.
Curiously and amusingly, another key developer on the team (who will remain unnamed as a professional courtesy) seemed to be terrified of being involved in this post when Gabe came over. When I stepped up to tell Gabe what to say, this developer looked totally relieved. I should have realized right there that I had a lot more influence that I suspected. Every time Gabe came over, it seemed like I was in the hot seat. Those were some challenging and amazing experiences!
A few weeks after this post went out, some very senior developers from Microsoft came by for a discreet visit. They loved our post, because it lit a fire underneath Microsoft's executives to get their act together and keep supporting Direct3D development. (Remember, at this point it was years since the last DirectX SDK release. The DirectX team was on life support.) Linux is obviously extremely influential.
It's perhaps hard to believe, but the Steam Linux effort made a significant impact inside of multiple corporations. It was a surprisingly influential project. Valve being deeply involved with Linux also gives the company a "worse case scenario" hedge vs. Microsoft. It's like a club held over MS's heads. They just need to keep spending the resources to keep their in-house Linux expertise in a healthy state.
I look back and now I see that I was totally not ready to handle the stress involved in this project. My ability and experience managing stress was very limited back then. I took on the lion's share of the graphics problems in the Source1 engine releases, I had to interact with the external driver teams and their managers/execs, help and present to external game developers about how to get good performance out of OpenGL, dodge patent attacks on my open source software, survive the rage of one corporation as I (naively!) helped their competitors implement support for a public GL extension, and also try to survive during the mass layoffs of 2013.
Unfortunately, these layoffs did impact the Linux team's morale and development efficiency. Even so, I did have a great time working at Valve overall. It was the most challenging and educational experience I've ever had. I highly doubt I could have gotten this kind of life changing experience at any other company.