Hypocrite Commits, Rust RFC & FUTEX2 Were Among Popular Kernel Topics In 2021

Written by Michael Larabel in Linux Kernel on 1 January 2022 at 12:49 PM EST. Add A Comment
There were a ton of exciting kernel improvements merged in 2021 as well as introducing new hardware support and more. But for as exciting as the year was, it actually ticked lower than usual on both a commit and line count basis. Here is a look at some of the popular kernel topics in 2021 as well as a look at the yearly Git development statistics.

As of yesterday when running GitStats on the Linux kernel source tree, the repository has seen 1,060,172 commits from around 24.3k different authors. The source tree currently is comprised of 32.2 million lines across 74.3k files.

The Linux kernel line count continues rising at a fairly consistent rate overall with the never-ending flow of new features and expanded hardware support reaching mainline.

While for as great as 2021 with features and hardware support, the kernel saw only 73.7k commits in 2021 -- down from 90.2k in 2020, 82.8k in 2019, 80.1k in 2018, etc. The last time there were 73k commits or less in a single year was all the way back in 2013 when it clocked in at 70.9k. Though partly for the offset is that in 2021 were 5 major kernel releases while some years have seen 6 major releases and in turn the extra merge window in that calendar year that leads to the big flow of new commits... Linux 5.16 meanwhile is out in a few weeks that in turn will kick off the Linux 5.17 merge window in January.

Besides far fewer commits than usual, in 2021 the Linux kernel saw 3.2 million lines added and 1.3 million lines removed, lower than 2020 that saw 4 million lines added with 1.5 million lines removed.

Linus Torvalds was the most prolific committer to the source tree, as usual. The next top five committers to the Linux kernel source tree were usual longtime prominent kernel contributors of David S. Miller, Arnd Bergmann, Christoph Hellwig, Lee Jones, and Jakub Kicinski.

In 2021 there were 4,421 different emails associated with Linux kernel commits, down from the 4,603 seen in 2020 but up compared to 2019 at 4,383.

Those curious about the Linux kernel GitStats in full for 2021 and prior years can see this dump with all the details.

In recapping the great features, proposed changes, and other kernel drama of 2021, the most popular kernel articles on Phoronix for the year included:

University Banned From Contributing To Linux Kernel For Intentionally Inserting Bugs
Greg Kroah-Hartman has banned a US university from trying to mainline Linux kernel patches over intentionally submitting questionable code with security implications and other "experiments" in the name of research.

Linus Torvalds Decides To Land NVIDIA RTX 30 "Ampere" Support In Linux 5.11
While new feature code is normally not allowed in past the end of the merge window for a given Linux kernel release cycle, Linus Torvalds has decided to merge the newly-published open-source driver code for the NVIDIA GeForce RTX 30 "Ampere" graphics cards for the Linux 5.11 kernel that will debut as stable in February.

IBM To Kernel Maintainer: "You Are An IBM Employee 100% Of The Time"
It's fairly common that many longtime Linux kernel developers use their personal email addresses for signing off on kernel patches or dealing with other patch work, especially when they are engaging with kernel development in their personal time too and occasionally jumping between employers over time while still sticking to interacting with the upstream kernel community, etc. There are also understandably some companies that mandate the use of their corporate email addresses for their official work/patches while now IBM seems to be taking things one step to the extreme.

Linux 5.13 Reverts + Fixes The Problematic University of Minnesota Patches
One month ago the University of Minnesota was banned from contributing to the Linux kernel when it was revealed the university researchers were trying to intentionally submit bugs into the kernel via new patches as "hypocrite commits" as part of a questionable research paper. Linux kernel developers have finally finished reviewing all UMN.edu patches to address problematic merges to the kernel and also cleaning up / fixing their questionable patches.

Btrfs Will Finally "Strongly Discourage" You When Creating RAID5 / RAID6 Arrays
For a number of years it has been known that the Btrfs RAID5 and RAID6 code is potentially unsafe and not nearly as mature as the native RAID support found in this Linux file-system for other levels. Finally now we are seeing the Btrfs user-space programs warn the user when attempting to create such Btrfs native RAID 5/6 configurations.

Linux Kernel Developers Discuss Dropping A Bunch Of Old CPUs
With Linux 5.10 having shipped as the latest Long Term Support (LTS) release to be maintained for at least the next five years, a discussion has begun over dropping a number of old and obsolete CPU platform support currently found within the mainline kernel. For many of the architectures being considered for removal they haven't seen any new commits in years but as is the case once proposals are made for them to be removed there are often passionate users wanting the support to be kept.

It Turns Out Windows Unconditionally Reserves The First 1MB Of RAM, Linux Was Just Late To Do So
Sent in last weekend to the Linux 5.13 kernel was the change so Linux x86/x86_64 will always reserve the first 1MB of RAM in order to avoid corruption issues with some BIOS and frame-buffers sometimes fiddling with that lowest portion of system memory. While the thought was reserving that first 1MB unconditionally was a bit onerous and that perhaps Windows has some way of determining how much low memory area to reserve, it turns out Windows has been employing this same behavior for years.

Axboe Achieves 8M IOPS Per-Core With Newest Linux Optimization Patches
It was just last week that Linux optimizations were leading to possible 6M IOPS per core and then at the start of this week new patches pushed Linux past 7M IOPS per-core with an ideal hardware configuration as well. In ending out the week, 8M IOPS has been reached!

"le9" Strives To Make Linux Very Usable On Systems With Small Amounts Of RAM
It's well known that the Linux desktop can be quite unbearable when under heavy memory pressure as has been showcased over the years and more attention these days turning to the likes of OOMD/systemd-oomd and other alternatives to better deal with Linux low/out-of-memory scenarios especially with today's desktop software and web browsers consuming increasing amounts of memory. Another effort coming to fruition for helping this scenario is the "le9" Linux kernel patches.

Linux x86/x86_64 Will Now Always Reserve The First 1MB Of RAM
The Linux x86/x86_64 kernel code already had logic in place for reserving portions of the first 1MB of RAM to avoid the BIOS or kernel potentially clobbering that space among other reasons while now Linux 5.13 is doing away with that "wankery" and will just unconditionally always reserve the first 1MB of RAM.

University of Minnesota Linux "Hypocrite Commit" Researchers Publish Open Letter
The drama in kernel land this week was University of Minnesota being banned from Linux kernel development over research they previously carried out looking at "hypocrite commits" and the possibility of intentionally introducing vulnerabilities (such as use-after-free bugs) into the kernel source tree. This weekend those researchers involved published an open letter to the Linux kernel community.

Linux 5.16 Will Be A Great Christmas Gift For Open-Source Fans With Many New Features
While Linux 5.15 isn't even making its debut for another week or two, there is already a lot to look forward to when it comes to Linux 5.16. Here is a look at some of the new features expected for the 5.16 cycle.

Linux 5.17 To Boast A Big TCP Performance Optimization
While the Linux 5.16 merge window just ended and that kernel won't be out until the tail end of the calendar year, already for Linux 5.17 new material is beginning to accumulate in the respective subsystem development trees... One set of changes merged this morning from Google can provide a sizable performance win around TCP performance in the datacenter.

The New NTFS File-System Driver Has Been Submitted For Linux 5.15
It looks like Paragon Software's NTFS3 kernel driver providing much better Linux support for the Microsoft NTFS file-system will land for the 5.15 kernel!

Linux Achieves 5.1M IOPS Per-Core With AMD Zen 3 + Intel Optane
Linux kernel developers have been working tirelessly to squeeze more performance out of IO_uring and the block / I/O code in general. IO_uring lead developer Jens Axboe who also serves as the Linux block subsystem's maintainer (among other roles and major contributions over the years) has used his system as a baseline for evaluating such kernel improvements. He's now moved to using AMD Zen 3 while sticking to Intel Optane storage and is seeing a mighty speed boost out of AMD's latest processors.

Samsung 860/870 SSDs Continue Causing Problems For Linux Users
While Samsung has explicitly stated before that queued TRIM works for Samsung 860 SSDs on Linux and thus leading to only older Samsung 840/850 drives being blocked from queued TRIM usage, that turns out to be inaccurate and now more quirks are added for the Samsung 860 and 870 series SSDs on Linux.

Linux 5.13 Released With Apple M1 Bringup, Landlock, FreeSync HDMI + Much More
Linus Torvalds has just released the Linux 5.13 kernel as stable.

Facebook Has Been Working On BOLT'ing The Linux Kernel For Greater Performance
For several years now Facebook engineers have been working on BOLT as a way to speed-up Linux/ELF binaries. This "Binary Optimization and Layout Tool" is able to re-arrange executables once profiled to generate even faster performance than what can be achieved by a compiler's LTO and PGO optimizations. One of the latest BOLT efforts has been on optimizing the Linux kernel image.

Updated Rust Code For Linux Kernel Patches Posted
In 2022 we will very likely see the experimental Rust programming language support within the Linux kernel mainlined. Sent out this morning were the updated patches introducing the initial support and infrastructure around handling of Rust within the kernel.

It Appears FUTEX2 Will Land For Linux 5.16
Barring any last minute reservations it appears the initial "FUTEX2" work that is of much interest to Linux gamers enjoying Steam Play / Proton will find that kernel functionality in Linux 5.16.
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About The Author
Michael Larabel

Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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