Development statistics for 6.19

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The 6.19 development cycle brought in the work from 2,141 developers, which just barely beats the previous record (2,134) set for 6.18; 333 of those developers made their first contribution to the kernel in 6.19, also a relatively high number. The most active developers for 6.19 were:

Most active 6.19 developers

By changesets Kuninori Morimoto 459 3.2% Christian Brauner 271 1.9% Johan Hovold 158 1.1% Ville Syrjälä 153 1.1% Ian Rogers 140 1.0% Russell King 124 0.9% Josh Poimboeuf 101 0.7% Andy Shevchenko 100 0.7% Krzysztof Kozlowski 93 0.6% Jani Nikula 91 0.6% Sean Christopherson 88 0.6% Filipe Manana 87 0.6% Marco Crivellari 87 0.6% Christoph Hellwig 86 0.6% Thomas Zimmermann 85 0.6% Eric Dumazet 85 0.6% Peter Zijlstra 82 0.6% Marc Zyngier 82 0.6% Frank Li 78 0.5% SeongJae Park 78 0.5%

By changed lines Miguel Ojeda 58000 7.8% Cyril Chao 19755 2.6% Christian Brauner 16604 2.2% YiPeng Chai 13293 1.8% Dmitry Baryshkov 12244 1.6% Ian Rogers 10933 1.5% Jason Gunthorpe 10851 1.5% Eric Biggers 9549 1.3% Daniel Scally 9429 1.3% AngeloGioacchino Del Regno 6201 0.8% Josh Poimboeuf 6010 0.8% Ilya Bakoulin 6009 0.8% Rob Herring 5777 0.8% Johannes Berg 5707 0.8% Svyatoslav Ryhel 5610 0.8% Akhil P Oommen 5516 0.7% Mauro Carvalho Chehab 5196 0.7% Neilay Kharwadkar 5162 0.7% Igor Belwon 5155 0.7% Lorenzo Stoakes 4830 0.6%

Kuninori Morimoto, who was first seen during the 2.6.28 development cycle in 2008, was the biggest contributor of changesets by virtue of a major refactoring effort in the sound subsystem. Christian Brauner, the maintainer of the virtual filesystem layer, refactored the handling of credentials, added the listns() system call, and added many self tests, among other contributions. Johan Hovold fixed numerous bugs and did a lot of cleanups in various driver subsystems. Ville Syrjälä worked extensively in the i915 graphics-driver subsystem, and Ian Rogers contributed a long list of improvements to the perf tool.

Looking at lines changed, Miguel Ojeda topped the list with the addition of a modified version of the Rust syn crate. Cyril Chao's first-ever kernel contribution, which put him into second place in the "lines-changed" list, was a driver for MediaTek mt8189 platform devices. YiPeng Chai worked with the amdgpu graphics driver, and Dmitry Baryshkov updated devicetree files for a number of Qualcomm devices.

A full 10% of the patches merged for 6.19 had Tested-by tags, while 56% had Reviewed-by tags; both of those numbers are slightly higher than usual. The top testers and reviews for this release were:

Test and review credits in 6.19
Tested-by Dan Wheeler 89 4.8% Joe Lawrence 63 3.4% Mark Brown 55 3.0% Randy Dunlap 53 2.9% Fuad Tabba 53 2.9% Lad Prabhakar 37 2.0% Shaopeng Tan 35 1.9% James Clark 34 1.8% Carl Worth 34 1.8% Hanjun Guo 33 1.8% Gavin Shan 32 1.7% Zeng Heng 32 1.7% Ryan Walklin 30 1.6% Kai Huang 29 1.6% Fenghua Yu 28 1.5% Yan Zhao 28 1.5%	Reviewed-by Charles Keepax 310 2.8% Dmitry Baryshkov 191 1.7% Geert Uytterhoeven 164 1.5% Frank Li 158 1.4% Krzysztof Kozlowski 156 1.4% David Sterba 144 1.3% Christoph Hellwig 139 1.3% Konrad Dybcio 125 1.1% Simon Horman 125 1.1% Ilpo Järvinen 118 1.1% Jan Kara 118 1.1% Jeff Layton 113 1.0% AngeloGioacchino Del Regno 111 1.0% Jonathan Cameron 109 1.0% Andrew Lunn 109 1.0% Ville Syrjälä 105 1.0%

The list of top reviewers is a bit different than in the past; somehow Charles Keepax managed to review 310 commits — more than four for every day of this 70-day release cycle — mostly within the sound-driver subsystem. The other top reviewers were focused on system-on-chip drivers and devicetree-related changes. The list of top testers is more typical, with Daniel Wheeler on top as usual.

The development of the 6.19 kernel was supported by 227 employers that we know of. The most active employers were:

Most active 6.19 employers

By changesets Intel 1591 11.1% (Unknown) 1410 9.8% Google 1099 7.7% Red Hat 829 5.8% Renesas Electronics 741 5.2% AMD 612 4.3% (None) 554 3.9% Qualcomm 485 3.4% SUSE 462 3.2% Microsoft 434 3.0% NVIDIA 407 2.8% (Consultant) 392 2.7% Meta 379 2.6% Oracle 371 2.6% NXP Semiconductors 325 2.3% Linaro 319 2.2% Huawei Technologies 260 1.8% IBM 236 1.6% Arm 200 1.4% Bootlin 160 1.1%

By lines changed Google 101728 13.6% (Unknown) 70125 9.4% Intel 59934 8.0% AMD 45025 6.0% Qualcomm 36322 4.9% NVIDIA 32585 4.4% Red Hat 31429 4.2% Microsoft 30621 4.1% (None) 27285 3.7% MediaTek 23223 3.1% Ideas on Board 14880 2.0% Renesas Electronics 14350 1.9% Meta 14232 1.9% Collabora 14088 1.9% Huawei Technologies 13257 1.8% SUSE 13209 1.8% Oracle 12943 1.7% Arm 12761 1.7% IBM 12230 1.6% Linaro 9015 1.2%

These numbers are reasonably consistent with recent history; hardware vendors are still contributing a large share of the changes. When considering which companies are most influential in kernel development, though, one should also look at the Signed-off-by tags added to patches by maintainers as they apply those patches to their repositories:

Non-author signoffs in 6.19

Individual Jakub Kicinski 991 7.5% Mark Brown 946 7.2% Andrew Morton 584 4.4% Alex Deucher 478 3.6% Greg Kroah-Hartman 406 3.1% Jens Axboe 277 2.1% Hans Verkuil 257 2.0% Bjorn Andersson 245 1.9% Paolo Abeni 218 1.7% Christian Brauner 200 1.5% Namhyung Kim 196 1.5% Shawn Guo 185 1.4% Martin K. Petersen 184 1.4% Peter Zijlstra 184 1.4% David Sterba 179 1.4% Jonathan Cameron 167 1.3% Alexei Starovoitov 141 1.1% Geert Uytterhoeven 129 1.0% Jonathan Corbet 121 0.9% Ilpo Järvinen 121 0.9%

By employer Meta 1544 11.8% Google 1296 9.9% Intel 1243 9.5% Arm 1171 8.9% AMD 848 6.5% Linaro 786 6.0% Red Hat 647 4.9% Qualcomm 564 4.3% Linux Foundation 441 3.4% Microsoft 432 3.3% SUSE 423 3.2% (Unknown) 409 3.1% NVIDIA 312 2.4% Cisco 257 2.0% Oracle 235 1.8% Huawei Technologies 233 1.8% (None) 209 1.6% LG Electronics 196 1.5% Renesas Electronics 174 1.3% IBM 133 1.0%

The top two companies here are both of the hyperscaler variety, with the top being Meta, which appears rather farther down in the list of changeset contributors. While Meta does contribute a lot of patches — and significant core patches at that — it also employs the maintainers that handle a lot more patches authored by others. Arm, too, shows a bigger influence by this metric.

Developer longevity

For as long as the kernel community has existed, people have worried about its ability to attract new developers. I have often pointed out that each release features the work of roughly 300 first-time developers; the response is often to ask how long those developers stay around. The time has come to try to give at least a partial answer to that question. The plot below was generated by accumulating a list of the 5,424 developers who made their first contribution to one of the 5.x mainline kernels, then looking at how many other releases each contributed to.

What we see is that 1,943 of those first-time contributors — 36% of the total — were never seen again after contributing to one release. Another 883 developers (16%) showed up for one other release, and so on. In the end, 32% of the first-time contributors during this period have been present for at least four kernel releases. At the long tail of the distribution, there are two first-time developers (Andrii Nakryiko and Vladimir Oltean) who have only missed one release and two (Stephan Gerhold and Stefano Garzarella) who have contributed to every release from 5.0 to 6.19.

To provide one other small data point: the first-time contributors being studied here arrived between early 2019 (the 5.0 release) and mid-2022 (5.19). Of those 5,424 developers, 1,067 (just under 20%) of them contributed to at least one of the releases made in 2025. It seems reasonable to consider that group as still being active in the kernel community. Whether these results are good or bad is probably a matter for debate, but it does seem clear that, while a lot of contributors pass through quickly, others are staying around for the long haul.

The kernel community as a whole is also clearly here for the long haul; the process shows no real signs of slowing down. As of this writing, there are just short of 11,000 changesets in the linux-next repository; most of those will move into the mainline in the upcoming merge window. The next kernel, which will be called 7.0, will continue to demonstrate the community's fast pace; stay tuned for the details.

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