LWN.net Weekly Edition for September 19, 2013

Why Steam on Linux matters for non-gamers

At LinuxCon North America 2013 in New Orleans, Gabe Newell from video game–maker Valve delivered a keynote talk explaining the company's interest in Linux. Although Valve does not expect Linux games to outsell those on proprietary operating systems in the near term, it sees several valuable side effects emerging from its Linux support efforts, and it predicts that in the long term, open systems built on Linux represent the future of gaming.

Linux Foundation executive director Jim Zemlin introduced Newell by observing that for many years critics had said that the thing holding back Linux adoption was the lack of good games. Now, however, they can no longer say so. Valve is one of the gaming industry's top players, and it has offered its Steam game-delivery platform for Linux since February 2013.

Newell opened his remarks by pointing out that Valve has produced games for a variety of device platforms: Windows, Mac OS X, the XBox, the Playstation, and so on. The Steam service is best known as an online content-delivery mechanism (to buy, download, and update games), but it also incorporates a suite of tools for game developers and users to create content. Valve has always recognized that as a company it will need to adapt to structural changes in the technology marketplace, he said, including the declining costs of computing and networking. The drop in these costs has led to a number of changes in the gaming marketplace, increasing the relative value of game design and decreasing the value of marketing and distribution.

Those changes have made digital distribution systems like Steam the new norm, but they have had unpredictable effects as well, such a the emergence of "free to play" games. At some point, he said, the marginal cost of adding a new player to the game falls below the marginal benefits that a new player adds to the game community, so it no longer needs to charge. Another example is the "electronic sports" phenomenon, where sites like Twitch.tv have arisen that operate as a game-driven economy that does not rely on game sales. While it would be nice to assume that this evolving marketplace will stop now that Valve is doing well financially, he said, the company realizes that things will just continue to change, which is why it feels Linux is important in the long run. Eventually, games themselves will become nodes in a connected economy where digital goods and content are created by individuals in the community.

Valve has had a long history with Linux, Newell continued. It first deployed Linux game servers (handling the back-end of multiplayer online games) in 1999, and Linux now accounts for the majority of all game servers. Internally, the company uses Linux in its development infrastructure, where it manages 20 terabytes of game data in version control. 20 terabytes sounds like a lot, he added, but the company moves around one exabyte of game data every year (not counting game servers), which accounts for two to three percent of global IP traffic.

Nevertheless, he said, Linux game players still account for less than one percent of Steam's users, and are insignificant by any metric. But the company has seen multiple knock-on effects since it first started working on Linux support in Steam. Working on Linux has improved graphics driver quality and has increased developer interest in Steam. But the openness of Linux is the factor that Valve considers the most important.

Several years ago, Newell said, the company became concerned about the direction that the PC industry was moving. Platform vendors rolled out systems that could be locked down, so that vendors could exert control over customers' machines. "If you didn't like Google, you could keep Google from installing on your platform." That line of thinking was seductive to platform vendors, but the result was a significant drop in year-over-year PC sales.

On the other hand, while PC sales have dropped, PC game sales have risen steadily. Ironically, this success in the gaming industry has been led by how much more open the PC platform is than the console industry—at least, on the hardware side. Proprietary hardware used to dominate game consoles, but commodity PC hardware based on open standards has evolved much faster and has displaced it. It is at the point now where gaming consoles re-use graphics hardware from PCs on the inside. PC gaming is where the real innovation happens, from social gaming to free-to-play to massively-multiplayer online games (MMOs)—and the rate of change is increasing.

The most significant innovation from Valve's perspective is the democratization of the gaming ecosystem. The "power" has shifted from console makers to game developers and now to end users. For example, he said, the Team Fortress community creates ten times the amount of code that Valve's paid developers do. "We're pretty cocky about how well we could compete with Bungie or other game makers," he said, "but the one group we can't compete with are our own users."

The community of users can already outproduce the company by an order of magnitude, he said, but if that is the trend, then proprietary systems are a problem because they create way too much friction in the process of creating and releasing content. For example, it can take six months to get Apple to approve an update to an existing iOS game; that is at odds with innovation. The company has concluded that closed systems are not the future of gaming: Linux is.

Of course, if Linux is the future of gaming as Valve had decided, the next logical question is what the company should do about that fact. It decided it had to put its efforts into making Linux a good solution both for gamers and for game developers. Initially, that effort was distressing, since there was so much work to be done. So the company decided to tackle it in stages, planning each stage with partners and customers.

The first step was getting its first game (Left 4 Dead 2) running on Linux, which Newell described as a "sweater thread of issues": there were problems with the NVIDIA driver, which revealed problems that the distributions needed to solve, which led to user experience problems. "'Just compile it yourself'," Newell said, "does not count as a solution for users." But the company persevered, and eventually it got Left 4 Dead 2 running on Linux, and running faster than it did on Windows. It discovered that many of the solutions it crafted for that game solved problems for its other games, too.

When Valve shipped its Steam client for Linux in February, Newell said, as much as anything, the action was a signal to its partners that the company was serious about Linux. It has since added to its stable of Linux games (totaling 198 as of now), but it has increased its Linux operations in other areas as well. It has committed engineers to Simple DirectMedia Layer (SDL) development and to the Khronos Group (which manages OpenGL and related standards), and it has started work on a Linux debugger—independent of the LLVM debugger effort, in which Valve also participates.

Newell closed by remarking that something the world has learned from the recent explosion of cloud computing is that once you abstract away certain particular problems, you recognize that the same abstraction should serve you everywhere. That is true of gaming as it is for other forms of computing, he said. Nobody thinks they should have to buy separate copies of games for the living room TV set and for their PC. Likewise, game developers do not think they should have to write separate input stacks for the different controllers found on the PC, the mobile device, and the living room game console. Valve thinks that Linux—and not proprietary platforms—can solve that problem. He promised to talk more about it "next week."

Game-industry watchers saw that final remark as a hint that Valve will be announcing a Linux-based console shortly. Whatever form such an announcement takes, Newell made it quite clear that the company sees Linux not just as a community of game-buyers to target, but as a technological platform on which it can develop products—and develop them faster and better than it can on the alternatives.

[The author would like to thank the Linux Foundation for assistance with travel to New Orleans.]

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Asteroid "mining" with Linux and FOSS

Planetary Resources is a company with a sky-high (some might claim "pie in the sky") goal: to find and mine asteroids for useful minerals and other compounds. It is also a company that uses Linux and lots of free software. So two of the engineers from Planetary Resources, Ray Ramadorai and Marc Allen, gave a presentation at LinuxCon North America to describe how and why the company uses FOSS—along with a bit about what it is trying to do overall.

Ramadorai, who is a Principal Avionics Engineer with the company, began the talk by relating that he joined the company by noticing that it was forming in Bellvue, Washington in 2012 and phoning the CEO. He started the talk with a question: what does asteroid mining have to do with Linux? It turns out, he said, that as they looked at the requirements for the spacecraft and compared it with those of a data center, there was a "lot of overlap" between the two. A spacecraft is a distributed system that requires high availability. In addition, power efficiency is important as the spacecraft are powered by solar panels. Using free software was an opportunity to use what's already been done in those areas, he said.

By way of some context, Ramadorai explained "why asteroids" and "why now". Technology has reached a point where it is viable to build small spacecraft capable of prospecting and eventually mining near-Earth objects (NEOs). Part of the reasoning is idealistic as many of the employees are "space fans", but there is also a significant opportunity for financial returns, he said.

There is more of an awareness about asteroids recently. The Russian meteor earlier this year is one example, but NASA in the US is also talking about capturing a NEO and orbiting it around the moon. There are a lot more launch opportunities these days due to the private space companies (e.g. SpaceX, Orbital Sciences). That means companies can get things to orbit for less than hundreds of millions of dollars. There has been a steady growth of the small satellite industry because of that. It's not so much that the price is coming down, but that there is much more capacity available for launches, he said.

Hardware has also gotten cheaper and more powerful. The MIPS per unit watt have been increasing, at least in standard (not space-rated) parts. There has been a lot of resistance within the aerospace industry to using off-the-shelf parts, but the cost and performance difference is huge. What's needed is a system that can handle some failures caused by space radiation.

It has gotten to the point where a small company can actually build and launch a spacecraft. FOSS has played a large role in that. The Planetary Resources software team is small, and Ramadorai estimates his team will only write 5-10% of the code that runs on the craft—the rest will come from existing free software.

He emphasized that this was a long-term endeavor for the company. Actually mining asteroids is a long way off. The first steps are to validate the technology by starting to prospect and visit NEOs. There are some 1.5 million asteroids larger than 1km in the solar system, with nearly 1000 of those being near Earth. If you look at smaller asteroids, those 100m or less, there are around 20,000 of them near Earth. Seventeen percent of those NEOs are "energetically closer" (i.e. require less energy to reach) than the Moon.

He showed some images of various NEOs that had been visited by probes, then showed one of the smallest on that slide (Itokawa) to scale with the Space Needle—it is wider than that building is tall (184m). The idea is that these are immense objects. They also can contain a great deal of interesting material. A 75m C-type asteroid has enough H₂ and O₂ to have launched all 135 Space Shuttle missions, while a 500m LL-Chondrite asteroid can contain more platinum than has been mined in human history.

Unfortunately, the US International Traffic in Arms Regulations (ITAR) restrict the kind of information Planetary Resources can share. Spacecraft are classified as munitions, which means that the company can't work with free software communities the way it would prefer to. The company strives to contribute as it can, while working within ITAR. It is "annoying" and in Ramadorai's opinion, "spacecraft should not be classified as munitions". He suggested that those interested "write Congress" about the problem.

The first step is the Arkyd 100 spacecraft that will be tested in low-Earth orbit. After that is the Arkyd 200 that will travel to Earth-crossing asteroids, and the Arkyd 300 that will actually land on asteroids. These are small craft; the Arkyd 100 can be relatively easily held by a human (say three shoe boxes in size).

Part of how they can be that small is by dual-purposing everything that can be. For example, the telescope that is used for prospecting and imaging asteroids is also used for laser communications with Earth. When a spacecraft is out 1-2 astronomical units (AUs), sending directional communication is a must for a low-power device. But at 2 AUs, the round-trip time is 32 minutes, so autonomy in the craft is essential.

The "state of the art" space-rated processor is the Rad750, a 32-bit PowerPC running at 133MHz. It uses 10 watts of power and costs $200,000. He compared that with an Intel Atom processor running at 1.6GHz, consuming 2 watts, and available for less than $1000. That is why the team is planning to use off-the-shelf parts and to deal with faults that will happen because the processor is not space rated.

Linux is important because they can run the same operating system on the craft, in the ground station systems, on their desktops, and in the cloud. The cloud is useful for doing simulations of the system code while injecting faults. It is common to spin up 10,000 instances in the cloud to do Monte Carlo simulations while injecting faults for testing purposes, he said.

Ramadorai then turned the floor over to Allen, who he described as one of the Jet Propulsion Laboratories (JPL) refugees at Planetary Resources. While at JPL, he worked on the backup landing software for the Curiosity Mars rover. He was, Ramadorai said, one of the few software people that was quite happy that his code never actually ran. Allen noted that he worked on flight software at JPL for five years, which gave him a different perspective than some others at the company; there is a "mix of both worlds" on the team.

Traditional deep space missions are expensive and take a long time to design and launch. There is a tendency to pick some technology (like the Rad750 processor) and stick with it. There are at most 2-3 vehicles built per project, but Planetary Resources has a different philosophy and set of motivations. It needs to look at "lots of asteroids" to find ones of interest.

That means using cheap, commodity hardware which can be upgraded as needed throughout the life of the project. Because the company is a low-cost spacecraft developer, it wants to use Linux and FOSS everywhere it can. Traditionally, each separate component was its own silo, so the software for flight, ground station, and operations were completely separate.

There is so much free software available that it is easy to find to reuse and repurpose for their needs, Allen said. The challenge is how to stitch all of the disparate pieces together into a high-availability system. But a proprietary system would have far fewer contributors and wouldn't get new features as quickly, he said.

For example, inter-process communication (IPC) has traditionally been created from scratch for each project, with custom messaging formats, state machines, and serialization mechanisms—all written from scratch. Instead of doing that, the Planetary Resources team specified a state machine model and message model in XML and fed it to some Python code that auto-generated the state machine and IPC code. It uses protobuf and Nanopb for serialization and ZeroMQ for message passing (among other FOSS components). "Why reinvent the wheel?", he asked.

That could not have been done in the past, because processors like the Rad750 would not support it. By using commodity hardware and handling faults when they occur, it opens up more possibilities. For example, a hypervisor is used to simulate redundant hardware in order to support triple modular redundancy. Three separate versions of the flight software can be run in virtual machines, voting on the outcome to eliminate a problem caused by space radiation in one of the programs. It isn't a perfect solution, but "we're not NASA, we don't have to have 100% reliability".

The team is considering putting a SQL database in the spacecraft itself. The communication availability, bandwidth, and reliability is such that there needs to be an easy and compact way for operations to request data sets to be retrieved. "Fundamentally, we a data company", Allen said, but much of the data will never reach Earth.

There are a number of challenges with maintaining database integrity in space. But there is only a need to make it "reliable enough" to be useful, corruption will happen, and the software must be designed with faults in mind. Using features like ECC memory or RAID for storage are two techniques that can be explored because of the flexibility that commodity hardware and FOSS provide.

Perhaps surprisingly, the cloud has been instrumental in developing the software. Simulating faults, stressing the software, and so on have all used the cloud extensively, he said. ITAR plays a role there too, as they must use Amazon's GovCloud, which is ITAR compliant.

Ramadorai wrapped things up with a quick pitch for anyone looking for employment. The company needs both hardware and software engineers; judging from the discussions going on after the talk, there were some interested folks in the audience.

The plan is to launch a prototype next year sometime, Ramadorai said. It is difficult to be more specific because launch dates (and carriers) frequently change. Beyond that, it would depend on how the early tests go. Mining asteroids is, alas, still quite a ways off it seems.

[ I would like to thank LWN subscribers for travel assistance to New Orleans for LinuxCon North America. ]

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WebKit, Blink, and the big split

The WebKit web rendering engine is used by free software projects of just about every flavor, from embedded Linux products to desktop browsers. Until recently, it was also the rendering engine that powered Google's Android and Chrome. At LinuxCon North America 2013 in New Orleans, Juan Sanchez from Igalia presented an inside look at the history of WebKit, and shared some thoughts on how the project will be affected by Google's decision to fork WebKit and create its own Blink engine.

Considering all the talk about HTML5 as the future of application development, Sanchez said, people talk surprisingly little about the actual components that go into delivering that future. WebKit is a key player, he explained. It is essentially the only practical choice for free software developers who want to embed web rendering into their code; Mozilla's Gecko is a highly capable rendering engine as well, but it is tied to the internals of Firefox in ways that make it less flexible for other uses. Igalia is one of the top contributors to WebKit; the company maintains the WebKitGTK+ "port" (a term with a specific meaning in the WebKit community) and it does a lot of consulting work for other companies which often includes embedding the WebKit engine.

The bird's eye kit

Sanchez reviewed the history of the project, and how the architecture of the code has evolved along with the community. WebKit started off as a fork of the KHTML renderer and KJS JavaScript engine from KDE. Apple began WebKit development in 2001, then opened the project up (with its contributions under a permissive BSD license) in 2005. WebKit's scope is limited: it just provides an engine that can understand and render HTML, CSS, JavaScript, and the Document Object Model (DOM), plus ways to interact with those web page contents. It does not attempt to be a browser on its own, and project members are not interested in turning WebKit into one. The project's focus is on compatibility: adhering to standards and providing components that are rigorously tested for compliance. As such, the project is pragmatic about its decision making—or as Sanchez put it, "WebKit is an engineering project, not a science project."

The entirety of what is commonly called WebKit consists of a few discrete parts, he said. There is the component called "WebKit," which simply provides a thin API layer for applications above it in the stack. Underneath this layer is "WebCore," which contains the rendering engine, page layout engine, and network access—the bulk of the functionality. In addition, there is a JavaScript engine (although which one is used varies from one WebKit-based application to another), and a platform-specific compatibility layer that hooks into general-purpose system libraries.

A "port" in WebKit is a version of WebKit adapted to specific target platform. The main ports maintained by the project are iOS, OS X, GTK+, Qt, EFL (for Tizen), and Google's Chromium. One new port is being discussed: WebKitNIX, which would be a lightweight port for OpenGL. But there are many smaller ports of WebKit as well, such as those for Symbian and Blackberry. To further illustrate how ports are designed, Sanchez explained how the WebKitGTK+ port is structured: The WebKit API layer becomes webkit/gtk, the JavaScript engine is JavaScriptCore, and the platform-specific compatibility layer calls out to GNOME components like libsoup, GStreamer, Cairo, and the Accessibility Toolkit (ATK).

Recent history and changes

In addition to the architecture described above, there is also another, known as WebKit2, which is currently in development. As Sanchez explained, WebKit2 is intended to replace the "WebKit" API layer, primarily to support a split-process model. In the new model, the user interface runs in one process, the main parsing and rendering of web content runs in a second process, and browser plugins run in a third. The goals are increased stability and performance, plus better security brought about by isolating the processes. Apple initiated the WebKit2 effort, and the code is currently working in the GTK+ and Qt ports as well. It is more-or-less complete, so that WebKit1 will move into maintenance mode shortly.

A major issue, however, is that WebKit2 is unrelated to Google's own work adapting Chrome to a split-process design. Chrome draws the "split process" barrier lower, so that each Chrome instance can have several rendering processes. This difference of opinion between Apple and Google goes back quite a ways, but it certainly contributed to Google's recent decision to fork WebKit and create Blink.

Another possible factor in the split related to project governance. The project has long had just two officially-defined roles: committer and reviewer. A committer must have sent in 20 to 30 patches and demonstrated a commitment to the project's rules: once designated a committer, a person can submit changes, although their changes are always reviewed. Becoming a designated reviewer is more difficult: around 300 patches are required, and three existing reviewers must vouch for the candidate. But once designated, a reviewer can commit changes directly, without review. More recently, though, Apple introduced the new top-level role of "owner," and declared that only owners would be allowed to commit changes to WebKit2.

Google abruptly left WebKit in April, via a surprise announcement that Sanchez said came as a shock to the WebKit community. Over the preceding years, as it had contributed to WebKit for Chrome, Google had risen to the point of equaling Apple in terms of the number of commits—each company contributed about one third of the changes to the code, with the remaining third coming from everyone else (Igalia included). In addition to the number of commits, Google actually had more engineers working on WebKit than did any other company (including Apple, who had fewer developers even though those developers produced as many patches as Google's).

WebKit from here on out

The divergence of Chrome and WebKit's multi-process model and Apple's desire to add a top-tier level of committer were both factors in Google's decision to start Blink, but there were other factors, too. Sanchez said that Google expressed its desire to simplify Blink's architecture, eliminating the concept of ports altogether and building the rendering engine specifically to suit Chrome's needs. The Blink code has already started to diverge, he said, and so far the Blink governance model is far simpler: there is no official code review, just people submitting changes and looking at others' changes informally. The majority of the Blink developers are Google employees, he said, but outside contributors have begun to appear, too.

Google's departure will certainly have an impact on WebKit, Sanchez said, although how much remains to be seen. The company obviously contributed a lot of code, so the developer-power will be missed, as will Google's ability to balance out Apple. With Apple as the largest remaining contributor to the project (and by a large margin), it will likely be more difficult for other companies or volunteers to have a say in steering the project.

The WebKit community is already seeing the impact of Google's departure in terms of orphaned modules that now need new maintainers. But there are also several instances of downstream projects dropping WebKit in favor of Blink. Sanchez noted that Opera had announced it would switch to WebKit just a few days before the Blink announcement; the company then issued a follow-up announcement announcing that it would be switching from WebKit to Blink. More recently, of course, Qt announced that it would adopt Blink as its HTML rendering engine, too.

On the other hand, Sanchez said, there were positive outcomes to Google's departure. Apple now seems likely to drop its proposal for a formal "owner" contributor role. There are also several hacks put into WebKit specifically for Chrome support that have already been removed. But that also means that the two rendering engines have already begun to diverge, and Sanchez said he was not sure how long code would remain portable between the two. It is good that free software developers now have two engines to choose from when creating an embedded web application, after so many years of WebKit being the only viable option. But the divergence could ultimately prove bad for the community, at least in some ways. Only time will tell.

[The author would like to thank the Linux Foundation for assistance with travel to New Orleans.]

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