Events: LCA Talks and ChefConf 2020 CFP

• The dark side of expertise

  Everyone has expertise in some things, which is normally seen as a good thing to have. But Dr. Sean Brady gave some examples of ways that our expertise can lead us astray, and actually cause us to make worse decisions, in a keynote at the 2020 linux.conf.au. Brady is a forensic engineer who specializes in analyzing engineering failures to try to discover the root causes behind them. The talk gave real-world examples of expertise gone wrong, as well as looking at some of the psychological research that demonstrates the problem. It was an interesting view into the ways that our brains work—and fail to work—in situations where our expertise may be sending our thoughts down the wrong path. Brady began his talk by going back to 1971 and a project to build a civic center arena in Hartford, Connecticut in the US. The building was meant to hold 10,000 seats; it had a large roof that was a "spiderweb of steel members". That roof would be sitting on four columns; it was to be built on the ground and then lifted into place.

• Poker and FOSS

  He introduced poker with a definition: "Poker is a gambling game of strategy played by people for money, using cards". The order of the terms in that definition is important, he said. In online poker, though, the "people" element is weakened because you can't see and directly interact with the other people you are playing with. So, unlike real-life poker, online poker is more about sociology than psychology; serious players track the trends of the player base as a whole, rather than trying to recognize the quirks of a particular person. That means online poker is "really about money". In order to succeed, one has to develop some weird views of the value of money. Even in games with relatively small stakes, players can win or lose a few thousand dollars in a session; in games with "nosebleed stakes", a player could be up or down by a million dollars in an evening. The game is particularly popular in the US, UK, and Australia, he said; it is played online and in face-to-face games in people's homes or at casinos. Poker became mainstream in the late 1990s, largely due to the "Late Night Poker" television series in the UK. There are a lot of different kinds of poker games, but the show focused on no-limit Texas hold 'em, which is the most "high drama of poker games" so it was well-suited to television. The show pioneered the use of a hole-card camera, so that viewers could see the two unseen cards each player was dealt. That innovation allowed viewers and commentators to analyze the choices that the players were making; without seeing the hole cards, watching other people play poker is about as interesting as "watching paint dry", Kuhn said. He did not go into the rules of poker much in the talk; a lot of it is not really germane to his topic. The important things to note are that it is a zero-sum, partial-information game where players are playing against each other and not the house (as they are in most other gambling games). It is a game of skill—better players win more over time—but there is a huge element of chance. In order for the house to make any money (casinos are not charities after all), a small percentage of the bets are kept by the house, which is usually called the "rake". All of that made poker an ideal candidate for online play. He put up a screen shot of a online poker game from 1999 and noted that all of today's poker sites have a similar look. It features a simple user interface that allows players to quickly and easily see the cards and make their bets. Most online poker players do not want sophisticated graphics and the like. So poker is relatively easy to write an online system for; there are a few "tricky bits", but in comparison to, say, an online multiplayer role-playing game, there are only minimal timing or network-delay issues to handle. It is completely turn-based and the state of the game is easily maintained on the server side. In addition, the client does not need any secret information, so the ability to cheat by extracting secrets from the data sent back and forth is eliminated—or, at least, it should be. The main problem for these systems is scaling them to accommodate as many tables as there is demand for. Serious players want to play in multiple games at once and the house maximizes its revenue by the number of games it can run. The "watershed moment" for online poker came in 2003 when Chris Moneymaker—his actual birth name, as has been documented—joined into a "satellite tournament" for the World Series of Poker (WSoP). Moneymaker paid $86 to enter the tournament and ended up winning the $10,000 entry into the main WSoP event in Las Vegas; he won that tournament and received $2.5 million for doing so. That created a huge boom in online poker, Kuhn said.

• ChefConf 2020 CFP – Make the Work Flow

  So hopefully you’ve taken the time to submit something. Lots of folks have, and thank you! Maybe you’re still not sure what you could talk about at ChefConf? Maybe you’ve got some interesting people stories from your time in the automation mines. Over the years we’ve categorized these talks as “DevOps” or “People, Processes, and Teams”, but the real guts of the discussion centers on how tooling helps people get their jobs done better, as well as how new theories in teamwork and product delivery impact technical teams. How we work together sets the stage for how we succeed together.

Graphics: Dav1d AV1 Acceleration, AMDVLK and Sway 1.4

• Dav1d AV1 Decoder Begins Adding AVX-512 Optimizations For Intel Ice Lake

  Ahead of the forthcoming dav1d 0.6 release, this open-source AV1 video decoder has begun implementing AVX-512 optimizations targeting Intel Ice Lake processors. The work has begun on AVX-512 optimizations focused on Ice Lake for this already quite speedy AV1 video decoder.

• AMDVLK 2020.Q1.1 Brings Some Performance Tuning, Still On Vulkan 1.1

  Out this morning is AMDVLK 2020.Q1.1 as AMD's first official open-source Vulkan driver code drop of the new year. While the Radeon Software Adrenalin Edition driver for Windows was recently updated with Vulkan 1.2 support, this AMDVLK release is still on Vulkan 1.1 but at least updated against API 1.1.130 compliance. Hopefully their next code drop will have the Vulkan 1.2 support officially exposed. Meanwhile Mesa's RADV Radeon Vulkan driver has been supporting Vulkan 1.2 since hours after the specification's unveil.

• Sway 1.4 Wayland Compositor Brings VNC Support, Initial Bits For MATE Panel Support

  Sway 1.4 is out today as the newest version of this i3-inspired Wayland compositor that has a growing following. Sway 1.4 consists of nearly 200 changes from over 50 contributors, showing the significant progress of this Wayland compositor that has been quick to pick-up features over the past few years.

LWN and Oracle on Linux 5.x Kernel

• Grabbing file descriptors with pidfd_getfd()

  In response to a growing desire for ways to control groups of processes from user space, the kernel has added a number of mechanisms that allow one process to operate on another. One piece that is currently missing, though, is the ability for a process to snatch a copy of an open file descriptor from another. That gap may soon be filled, though, if the pidfd_getfd() system-call patch set from Sargun Dhillon is merged. One thing that is possible in current kernels is to open a file that another process also has open; the information needed to do that is in each process's /proc directory. That does not work, though, for file descriptors referring to pipes, sockets, or other objects that do not appear in the filesystem hierarchy. Just as importantly, though, opening a new file in this way creates a new entry in the file table; it is not the entry corresponding to the file descriptor in the process of interest. That distinction matters if the objective is to modify that particular file descriptor. One use case mentioned in the patch series is using seccomp to intercept attempts to bind a socket to a privileged port. A privileged supervisor process could, if it so chose, grab the file descriptor for that socket from the target process and actually perform the bind — something the target process would not have the privilege to do on its own. Since the grabbed file descriptor is essentially identical to the original, the bind operation will be visible to the target process as well. For the sufficiently determined, it is actually possible to extract a file descriptor from another process now. The technique involves using ptrace() to attach to that process, stop it from executing, inject some code that opens a connection to the supervisor process and sends the file descriptor via an SCM_RIGHTS datagram, then running that code. This solution might justly be said to be slightly lacking in elegance. It also requires stopping the target process, which is likely to be unwelcome.

• configfd() and shifting bind mounts

  The 5.2 kernel saw the addition of an extensive new API for the mounting (and remounting) of filesystems; this article covered an early version of that API. Since then, work in this area has mostly focused on enabling filesystems to support this API fully. James Bottomley has taken a look at this API as part of the job of redesigning his shiftfs filesystem and found it to be incomplete. What has followed is a significant set of changes that promise to simplify the mount API — though it turns out that "simple" is often in the eye of the beholder. The mount API work replaces the existing, complex mount() system call with a half-dozen or so new system calls. An application would call fsopen() to open a filesystem stored somewhere or fspick() to open an already mounted filesystem. Calls to fsconfig() set various parameters related to the mount; fsmount() is then called to mount a filesystem within the kernel and move_mount() to attach the result to the filesystem hierarchy somewhere. There are a couple more calls to fill in other parts of the interface as well. The intent is for this set of system calls to be able to replace mount() entirely with something that is more flexible, capable, and maintainable. Back in November, Bottomley discovered one significant gap with the new API: it is not possible to use it to set up a read-only bind mount. The problem is that bind mounts are special; they do not represent a filesystem directly. Instead, they can be thought of as a view of a filesystem that is mounted elsewhere. There is no superblock associated with a bind mount, which turns out to be a problem where the new API is concerned, since fsconfig() is designed to operate on superblocks. An attempt to call fsconfig() on a bind mount will end up modifying the original mount, which is almost certainly not what the caller had in mind. So there is no way to set the read-only flag for a bind mount. David Howells, the creator of the new mount API, responded that what is needed is yet another system call, mount_setattr(), which would change attributes of mounts. That would work for the read-only case, Bottomley said, but it falls down when it comes to more complex situations, such as his proposed UID-shifting bind mount. Instead, he said, the file-descriptor-based configuration mechanism provided by fsconfig() is well suited to this job, but it needs to be made more widely applicable. He suggested that this interface be made more generic so that it could be used in both situations (and beyond).

• Accelerating netfilter with hardware offload, part 1

  Supporting network protocols at high speeds in pure software is getting increasingly difficult, with 25-100Gb/s interfaces available now and 200-400Gb/s starting to show up. Packet processing at 100Gb/s must happen in 200 cycles or less, which does not leave much room for processing at the operating-system level. Fortunately some operations can be performed by hardware, including checksum verification and offloading parts of the packet send and receive paths. As modern hardware adds more functionality, new options are becoming available. The 5.3 kernel includes a patch set from Pablo Neira Ayuso that added support for offloading some packet filtering with netfilter. This patch set not only adds the offload support, but also performs a refactoring of the existing offload paths in the generic code and the network card drivers. More work came in the following kernel releases. This seems like a good moment to review the recent advancements in offloading in the network stack.

• Linux Kernel Developments Since 5.0: Features and Developments of Note

  Last year, I covered features in Linux kernel 5.0 that we thought were worth highlighting. Unbreakable Enterprise Kernel 6 is based on stable kernel 5.4 and was recently made available as a developer preview. So, now is as good a time as any to review developments that have occurred since 5.0. While the features below are roughly in chronological order, there is no significance to the order otherwise. BPF spinlock patches BPF (Berkeley Packet Filter) spinlock patches give BPF programs increased control over concurrency. Learn more about BPF and how to use it in this seven part series by Oracle developer Alan Maguire. Btrfs ZSTD compression The Btrfs filesystem now supports the use of multiple ZSTD (Zstandard) compression levels. See this commit for some information about the feature and the performance characteristics of the various levels. Memory compaction improvements Memory compaction has been reworked, resulting in significant improvements in compaction success rates and CPU time required. In benchmarks that try to allocated Transparent HugePages in deliberatly fragmented virtual memory, the number of pages scanned for migration was reduced by 65% and the free scanner was reduced by 97.5%.