Statistics from the 5.18 development cycle
The 5.18 development cycle saw the addition of 14,954 non-merge changesets from 2,024 developers, 289 of whom made their first kernel contribution during this time. None of these numbers are records, though the number of developers came close to the maximum seen so far (2,062 for 5.13). This work resulted in the addition of 756,00 lines of code to the kernel.
The top contributors to 5.18 were:
Most active 5.18 developers
By changesets Krzysztof Kozlowski 214 1.4% Matthew Wilcox 164 1.1% Christoph Hellwig 154 1.0% Geert Uytterhoeven 140 0.9% Ville Syrjälä 135 0.9% Jonathan Cameron 119 0.8% Andy Shevchenko 118 0.8% Lorenzo Bianconi 117 0.8% Vladimir Oltean 111 0.7% Hans de Goede 110 0.7% Martin Kaiser 110 0.7% Colin Ian King 104 0.7% Sean Christopherson 100 0.7% Jakub Kicinski 100 0.7% Christophe JAILLET 89 0.6% Michael Straube 87 0.6% Jani Nikula 86 0.6% Trond Myklebust 81 0.5% Eric Dumazet 80 0.5% Christophe Leroy 80 0.5%
By changed lines Leo Li 227676 19.4% Qingqing Zhuo 197757 16.9% Ian Rogers 72008 6.1% Alan Kao 15814 1.3% Ming Qian 12176 1.0% Linus Walleij 8881 0.8% Krzysztof Kozlowski 8844 0.8% Dimitris Michailidis 8791 0.7% Christoph Hellwig 7165 0.6% Matt Roper 7114 0.6% Jakub Kicinski 7040 0.6% Jacob Keller 6877 0.6% Geert Uytterhoeven 6039 0.5% Ranjani Sridharan 5768 0.5% Evan Quan 5232 0.4% Guodong Liu 4944 0.4% Mauro Carvalho Chehab 4816 0.4% Vladimir Oltean 4776 0.4% Brett Creeley 4660 0.4% Adrian Hunter 4651 0.4%
Krzysztof Kozlowski is the developer who contributed the most patches to 5.18; this work consisted mainly of device-tree updates. Matthew Wilcox managed to get another set of folio patches merged. Christoph Hellwig continues to massively refactor the block and filesystem layers. Geert Uytterhoeven contributed a large set of Renesas pin-control improvements, and Ville Syrjälä did a lot of work on the Intel i915 graphics driver.
In the "changed lines" column, Leo Li added over 200,000 lines with just five patches adding register definitions for the AMD graphics driver — and Qingqing Zhuo added nearly 200,000 more. Ian Rogers made a number of improvements to the perf tool, Alan Kao contributed a single patch removing the nds32 architecture, and Ming Qian contributed a set of Amphion media drivers.
The top testers and reviewers of patches were:
Test and review credits in 5.18
Tested-by Daniel Wheeler 155 11.7% Damien Le Moal 77 5.8% Konrad Jankowski 54 4.1% David Howells 53 4.0% Mike Marshall 53 4.0% Gurucharan 38 2.9% Marc Zyngier 32 2.4% Vladimir Murzin 32 2.4% Randy Dunlap 21 1.6% Jiri Olsa 17 1.3% Julian Grahsl 16 1.2% Yihang Li 15 1.1%
Reviewed-by Rob Herring 217 2.7% Christoph Hellwig 204 2.6% Andy Shevchenko 143 1.1% AngeloGioacchino Del Regno 110 1.4% Stephen Boyd 103 1.3% Pierre-Louis Bossart 103 1.3% Alex Deucher 98 1.2% Krzysztof Kozlowski 96 1.2% Hans de Goede 91 1.1% Péter Ujfalusi 88 1.1% Jani Nikula 86 1.1% Himanshu Madhani 85 1.1%
Daniel Wheeler continues to receive the most test credits, having applied Tested-by tags to many AMD graphics-driver patches. It's worth noting that Wheeler posts occasional summaries describing the testing that has been done. Damien Le Moal tested many of the folio patches. and Konrad Jankowski regularly tests Intel network-driver patches.
Turning to the review column, Rob Herring routinely reviews device-tree patches. Christoph Hellwig reviewed patches in the block and filesystem subsystems — and a number of the folio patches as well. Andy Shevchenko reviewed many driver patches, mostly in the I2C, GPIO, and pin-control subsystems.
In the past it has been easy to be cynical about these numbers; they didn't capture much of the test and review activity happening in the community and were easily gamed. There is still surely a lot of work going on that is not reflected above, but it would be hard to argue that the testers and reviewers on these lists don't belong there. Perhaps this reflects a greater understanding of the value of these activities on the part of developers and (especially) their employers.
Whether the same can be said for bug reporting will be left for the reader to decide:
Top bug-report credits for 5.18 kernel test robot 232 19.3% Zeal Robot 76 6.3% Syzbot 72 6.0% Abaci 62 5.2% Dan Carpenter 29 2.4% Hulk Robot 27 2.2% Stephen Rothwell 26 2.2% Igor Zhbanov 19 1.6% Randy Dunlap 12 1.0% Rob Herring 9 0.7%
Bug reporting is clearly a job for robots these days. But note that, while 2,249 5.18 patches were backported to the 5.17 stable updates (so far), only 1,075 contained Reported-by tags. That would suggest that that just over half of the fixes being applied do not carry those tags and that, probably, a number of bug reports are going without credit.
The employers contributing most actively to this development cycle were:
Most active 5.18 employers
By changesets Intel 1708 11.4% (Unknown) 1155 7.7% Red Hat 958 6.4% 886 5.9% (None) 818 5.5% AMD 781 5.2% Linaro 560 3.7% Huawei Technologies 471 3.1% 446 3.0% NVIDIA 396 2.6% (Consultant) 363 2.4% SUSE 344 2.3% IBM 334 2.2% Oracle 325 2.2% Arm 294 2.0% Renesas Electronics 262 1.8% MediaTek 249 1.7% NXP Semiconductors 236 1.6% Canonical 227 1.5% Microchip Technology 201 1.3%
By lines changed AMD 467642 39.9% Intel 107081 9.1% 103801 8.8% (Unknown) 49669 4.2% Linaro 29631 2.5% Red Hat 28807 2.5% (None) 27989 2.4% NXP Semiconductors 21418 1.8% NVIDIA 19203 1.6% MediaTek 18980 1.6% 16036 1.4% Andes Technology 15814 1.3% (Consultant) 14314 1.2% Huawei Technologies 13483 1.1% IBM 11960 1.0% Microchip Technology 11853 1.0% Renesas Electronics 11427 1.0% SUSE 10128 0.9% Canonical 8984 0.8% Fungible 8791 0.7%
As usual, there are few surprises here.
![[Patch-flow plot]](https://static.lwn.net/images/2022/treeplot-5.18.svg)
Patch flow and signed tags
The illegible plot on the right (click to be able to actually read it) shows the paths taken by patches into the mainline kernel. Each box represents a Git repository, with the vectors showing the movement of patches from one repository to the next. This plot, which was generated by the treeplot utility from the gitdm collection of hacks (available from git://git.lwn.net/gitdm.git), provides an overall picture of how code moves through the maintainer community.
That picture remains relatively flat; most maintainers push their changes directly to Linus Torvalds. There is, however, a steady growth in the role of intermediate repositories, with the biggest ones handling the networking, graphics, system-on-chip, and character driver subsystems. The plot is a schematic diagram of the machine that has allowed the kernel process to scale to its current size — and, presumably, beyond.
The color of each vector indicates whether that repository is using signed tags on patches being pushed to the next level in the hierarchy; red lines indicate the lack of such a tag. The use of GPG signatures on tags allows a receiving maintainer to verify that a pull request was created by the person it claims to be from. If all pull requests include signed tags, it will be significantly harder for an attacker to convince a maintainer to pull from a malicious branch.
As has been documented here over the years, that universal use of signed tags has been slow to happen. Recently, though, Torvalds has become more insistent, with explicit requests to recalcitrant maintainers to get with the program. The end result is that, for 5.18, only 714 patches did not come from a signed tag — and 565 of those were directly applied by Torvalds and didn't arrive via a Git repository at all. So, at the top level of the tree, the switch to using signed tags is nearly complete — a mere 11 years after the practice was adopted. Some of the mid-level maintainers are still clearly not requiring signed tags on pull requests, though, so there are still some holes in the process.
Older bugs
Many of the patches applied to 5.18 fix bugs; how old are those bugs? One way of approximating an answer to that question is to look at how many fixes showing up in the stable updates were first applied to 5.18. A bug fix, one would expect, will not be backported beyond the release that introduced the bug in the first place. The results for 5.18 are:
Release Backports 5.17 (Mar 2022) 2,249 5.15 (Oct 2021) 1,762 5.10 (Dec 2020) 1,185 5.4 (Nov 2019) 756 4.19 (Oct 2018) 532 4.14 (Nov 2017) 422 4.9 (Dec 2016) 331
As can be seen above, 331 fixes (so far) have been ported from 5.18 all the way back to the 4.9 kernel, which was released over five years ago. In other words, after more than five years of intensive fixing (stable updates to 4.9 have added nearly 22,000 fixes), we are still fixing nearly five bugs in 4.9 every day. We'll get that kernel right one of these years, probably just before its end of life date.
To summarize, the kernel machine continues to move at high speed. Lots of
bugs are being fixed and, beyond doubt, lots more are being introduced.
The end result continues to be the kernel that we all rely on.
| Index entries for this article | |
|---|---|
| Kernel | Releases/5.18 |