Linux 3.14 Upgrades ZRAM, Buffer Features

Linus Torvalds, the creator of Linux, formally released the Linux 3.14 kernel on 30 March. The new 3.14 Linux kernel follows the Linux 3.13 kernel that was released in January.

Given that the new kernel carries the release number 3.14, which is a number that is also well-known as the mathematical Pi constant, there was early speculation that Torvalds might name the new kernel Pi. Torvalds dismissed this idea early on in the Linux 3.14 development process.

‘Shuffling zombie juror’

“I realise that as a number, 3.14 looks familiar to people, and I had naming requests related to that. But that’s simply not how the nonsense kernel names work,” Torvalds wrote in his announcement for the first release candidate of Linux 3.14 . “Besides, any self-respecting geek will know pi to twenty decimal places from their dorky youth, so 3.14 isn’t really that close, is it?”

The kernel is, in fact, nicknamed “shuffling zombie juror”, but Torvalds said Pi fans should not dispair. “You can console yourself with the fact that the name doesn’t actually show up anywhere, and nobody really cares,” he wrote. “So any pi-related name you make up will be *quite* as relevant as the one in the main Makefile.”

There was also some early speculation that the Linux 3.14 kernel might be released on Pi Day, 14 March (3/14), but that also didn’t happen. The Linux 3.14 kernel went through a total of eight release candidates prior to the final release.

“We had a few fairly late changes that I could have done without, but the changelog from -rc8 [release candidate 8] is still pretty small, and I’m feeling pretty good about it all,” Torvalds wrote in his release announcement for the Linux 3.14 kernel. “If we did end up with any last-minute problems due to the final spurt of patches, they’ll be pretty specific, and it really didn’t make sense to me to delay the release without anything known pending.”

ZRAM memory compression

Among the new features that is landing in the Linux 3.14 kernel is support for ZRAM memory compression technology. While ZRAM is only now officially landing as a stable technology that is directly integrated with the Linux kernel, it is a technology that is already deployed by Google in its ChromeOS and Android 4.4 operating systems. ZRAM has actually been in the Linux kernel staging development branch since the Linux 2.6.33 kernel, which was first released in February 2010.

Linux kernel developer Minchan Kim noted in his kernel code commit message for ZRAM that the technology has been in the development stage for a long time while the code was improved and stabilised. According to Kim, the benefits of ZRAM are clear and have particular impact for video use cases. In Kim’s experience, ZRAM compression has been able to improve video by reducing playback jitter, through relieving memory pressure.

PIE code

While Torvalds did not name the Linux kernel Pi, nor did he release the 3.14 kernel on Pi Day, there is in fact still PIE, or proportional integral controller enhanced, code within Linux 3.14.

With the new Linux 3.14 kernel, developers have also taken aim at solving a problem known as “buffer bloat”.

“Buffer bloat is a phenomenon where excess buffers in the network cause high latency and jitter,” Linux kernel developer Vijay Subramanian wrote in his kernel commit message. “As more and more interactive applications [e.g., voice over IP, real time video streaming and financial transactions] run in the Internet, high latency and jitter degrade application performance.”

To solve the challenge of buffer bloat in the Linux kernel, the PIE code has been integrated to solve the problem. PIE was first proposed in an Internet Engineering Task Force (IETF) draft in June 2013.

“Simulation results, theoretical analysis and Linux test bed results have shown that PIE can ensure low latency and achieve high link utilisation under various congestion situations,” the IETF draft states.

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Originally published on eWeek.