Linux has Real-Time now. What the fart does that actually mean?

Summary

The video discusses a significant update in the Linux kernel, with the merging of the 'preempt RT' feature, enabling real-time support after 20 years of development. This update is crucial for applications requiring extreme predictability and low latency, such as robotics, medical devices, and audio/video production. While real-time Linux guarantees a maximum response time for high-priority tasks, it's not designed to boost general performance and may even slow down everyday tasks. The update was symbolically delivered to Linus Torvalds, wrapped in gold and a ribbon, marking a milestone for Linux development.

Takeaways

• 🔧 Linus Torvalds merged the long-awaited real-time (RT) support into the Linux kernel after 20 years of development.
• 🖥️ The preempt RT enables real-time preemption, crucial for high-priority processes that require strict response times in Linux.
• ⏳ Real-time Linux doesn’t necessarily make Linux faster but ensures reliable maximum response times for high-priority tasks.
• 🚗 This feature is highly beneficial for critical applications such as self-driving cars, where decisions need to be made immediately.
• 🎧 Realtime Linux is particularly useful for audio/video production, offering better reliability in syncing audio/video streams.
• ⚕️ Other real-world applications include medical equipment, precision robotics, and embedded systems that require immediate, predictable responses.
• 🛠️ A key hurdle in RT kernel development was the printk debugging tool, which initially interfered with real-time performance but has been resolved.
• 📅 Development started in the 1990s, but the current version of the Linux RT project began on September 20, 2004, making it a 20-year journey.
• 🏅 While real-time support is essential for specific industries, most average Linux users and gamers won’t see a benefit from using the RT kernel.
• 🎁 The code for real-time Linux was humorously presented to Linus Torvalds at the Linux Plumbers Conference, wrapped in gold paper and a ribbon.

Q & A

What is the significance of the recent code change merged into the Linux kernel by Linus Torvalds?

The code change enables full realtime (RT) support in the Linux kernel, which guarantees extremely low and predictable latency for high-priority processes. This is a significant development for certain specialized applications, such as medical devices, robotics, and audio/video production.

What does 'preempt RT' mean in the context of the Linux kernel?

Preempt RT (realtime preemption) allows the Linux kernel to prioritize high-priority processes with predictable maximum response times. It ensures that tasks requiring immediate attention can preempt other tasks without delay, which is crucial for realtime systems.

Will the new realtime support make Linux faster for most users?

No, the realtime support in Linux does not make it faster for most users. In fact, in some cases, it can make Linux slower. Its main advantage is ensuring predictability and low latency for specific high-priority processes, not overall system speed.

What types of applications will benefit from realtime Linux support?

Applications such as medical equipment, precision robotics, automotive systems (e.g., self-driving cars), and audio/video production will benefit from realtime Linux support. These require extremely low latency and reliable response times for critical operations.

How does the realtime Linux kernel improve system reliability for high-priority tasks?

The realtime Linux kernel sets a maximum response time for high-priority tasks, allowing developers to build systems with predictable performance. This ensures that critical tasks, like avoiding obstacles in self-driving cars or precise audio syncing, can be handled without unexpected delays.

Why did it take over 20 years to enable full realtime support in the mainline Linux kernel?

The delay was primarily due to the complexity of integrating realtime preemption with existing kernel functions, particularly 'printk,' a debugging tool. Printk's behavior, which gives it priority over other processes, had to be adjusted to fit the requirements of a realtime system.

What role did the 'printk' function play in delaying the merge of preempt RT into the mainline Linux kernel?

Printk is a debugging tool that interjects itself into the process flow, causing delays, which is problematic for realtime systems that need to minimize latency. Resolving this issue took years of negotiation and technical changes to finally allow preempt RT to be integrated into the kernel.

What is the significance of the gesture of wrapping the code changes in gold paper at the Linux Plumbers Conference?

The gesture was symbolic. Linus Torvalds had humorously requested that the realtime code be delivered to him wrapped in gold when it was ready. At the Linux Plumbers Conference, developers physically presented the code changes in gold paper with a purple ribbon, marking the long-awaited milestone.

Will most Linux users need or use the realtime version of the Linux kernel?

No, most regular Linux users will not need or use the realtime version of the Linux kernel. Realtime Linux is specifically useful for embedded systems, medical devices, robotics, and professional audio/video production but offers little to no benefit for general desktop use.

What are some use cases where realtime Linux is already being used?

Realtime Linux is already in use in embedded systems, medical devices, and professional audio/video equipment. For example, it has been employed in audio processing systems that require precise timing and low-latency audio synchronization.