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Linux 4.19 Improves Containers, Latency and Networking for the Long Term

By Sean Michael Kerner (Send Email)
Posted October 22, 2018


The Linux 4.19 kernel was released on Oct. 22, bringing with it a host of new features for servers large and small. Linux 4.19 is the fifth major Linux kernel released in 2018 and follows the 4.18 kernel, which became generally available on Aug. 12.

The Linux 4.19 release cycle was a bit more dramatic than the other four releases in 2018 as Linux creator Linus Torvalds stepped away from the release during the development cycle to work on his own interpersonal behavior and conduct. As such, the final release was made by Linux stable branch maintainer Greg Kroah-Hartman.

"While it was not the largest kernel release ever by number of commits, it was larger than the last 3 releases, which is a non-trivial thing to do," Kroah-Hartman wrote in his release message. "After the original -rc1 bumps, things settled down on the code side, and it looks like stuff came nicely together to make a solid kernel for everyone to use for a while. And given that this is going to be one of the 'Long Term' kernels I end up maintaining for a few years, that's good news for everyone."

A Long Term kernel is maintained and supported by the upstream stable Linux community for at least two years. The last Linux kernel to gain the Long Term support designation was Linux 4.14, which was released in November 2017.

Improved Latency

Among the big new features in Linux 4.19 is a block I/O latency controller that aims to provide a minimum I/O latency target for defined control groups (cgroups).

"This is a cgroup v2 controller for IO workload protection," Facebook developer Josef Bacik wrote in his Linux commit message. "You provide a group with a latency target, and if the average latency exceeds that target, the controller will throttle any peers that have a lower latency target than the protected workload."

Memory Improvements for Containers

The overlaysfs first landed in the Linux 3.8 kernel that was released in December 2014, providing an overlay on top of the existing system filesystem, on which a container engine can run without needing to interact with the base filesystem.

In Linux 4.19, overlayfs benefits from multiple memory usage improvements that should serve to help accelerate container workload operations.

Improving Networking with CAKE

The Common Applications Kept Enhanced (CAKE) queue management algorithm also makes its debut in Linux 4.19, providing an improved approach for network packet scheduling.

"sch_cake targets the home router use case and is intended to squeeze the most bandwidth and latency out of even the slowest ISP links and routers, while presenting an API simple enough that even an ISP can configure it," Linux kernel developer Toke Høiland-Jørgensen wrote in his commit message.

Sean Michael Kerner is a senior editor at ServerWatch and InternetNews.com. Follow him on Twitter @TechJournalist.

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