4.1 development statistics

With 11,664 changesets merged as of 4.1-rc6, this cycle is a little bit slower than most that have been seen in the last year, though it is significantly busier than 4.0, which finished with 10,346 changesets. The number of developers involved, at 1,492, comfortably exceeds 4.0; indeed, it currently ties 3.15 for the title of the most developers ever. Chances are good that, by the time it is released, the 4.1 kernel cycle will be the first to see the participation of over 1,500 developers. Of those over 1,500 developers, 270 have contributed their first patch ever in this cycle — a fairly typical number for recent years.

Those developers have added 486,000 lines of code and removed 286,000 lines, for a net growth of 200,000 lines this time around. The most active developers doing this work were:

Most active 4.1 developers

By changesets Ian Abbott 129 1.1% Takashi Iwai 121 1.0% Hans Verkuil 119 1.0% Marcel Holtmann 117 1.0% Aya Mahfouz 107 0.9% Geert Uytterhoeven 105 0.9% Laurent Pinchart 102 0.9% Richard Weinberger 95 0.8% Joe Perches 92 0.8% Eric Dumazet 92 0.8% Al Viro 90 0.8% Krzysztof Kozlowski 77 0.7% Fabian Frederick 77 0.7% Benjamin Romer 74 0.6% Jiri Olsa 73 0.6% Denys Vlasenko 72 0.6% Mauro Carvalho Chehab 67 0.6% Nicholas Mc Guire 66 0.6% Guenter Roeck 65 0.6% Lars-Peter Clausen 65 0.6%

By changed lines Jie Yang 20194 3.4% Stephen Boyd 13536 2.3% Sudip Mukherjee 10198 1.7% Chanwoo Choi 8571 1.5% Heiko Carstens 8239 1.4% Tomeu Vizoso 7647 1.3% Hongzhou Yang 7391 1.3% Joe Perches 7135 1.2% Laurent Pinchart 6589 1.1% J. German Rivera 6359 1.1% Takashi Iwai 6173 1.0% Magnus Damm 6082 1.0% Mathieu Poirier 5915 1.0% Michael Ellerman 5874 1.0% Ray Jui 5362 0.9% Andy Shevchenko 4857 0.8% Hai Li 4487 0.8% Andrew Bresticker 4252 0.7% Markus Stockhausen 4221 0.7% James Hogan 4172 0.7%

Hartley Sweeten no longer tops out the list with his Comedi driver work but, never fear, Ian Abbott contributed the most 4.1 changesets by working on, yes, the Comedi drivers. Remember, though, that Hartley contributed 463 Comedi changes in 3.19, so it may well be that work on this code is finally slowing down, though there doesn't appear to be a plan to move it out of the staging tree quite yet. Takashi Iwai is the sound subsystem maintainer, so most of his work concentrates in that area; for similar reasons, it is unsurprising that Hans Verkuil's changes were all found within the media subsystem and Marcel Holtmann's patches were applied to the Bluetooth code. Aya Mahfouz, instead, is an intern in the Outreachy project's current round; she has clearly gotten off to a strong start with a lot of cleanup patches applied to staging drivers.

On the "lines changed" side, Jie Yang's work was mostly a reorganization of the Intel audio driver code. Stephen Boyd removed some old ARM drivers, making him the developer having removed the most code in this development cycle. Sudip Mukherjee did a bunch of cleanupv work on a number of staging drivers, Chanwoo Choi worked mostly on the Samsung Exynos clock drivers, and Heiko Carstens removed a bunch of relatively obscure S/390 code — such as 31-bit support.

There were (at least) 215 employers supporting work on the 4.1 kernel, the most active of which were:

Most active 4.1 employers

By changesets Intel 1308 11.2% Red Hat 1069 9.2% (None) 1055 9.0% (Unknown) 950 8.1% SUSE 437 3.7% Linaro 387 3.3% IBM 385 3.3% Outreachy 381 3.3% Google 362 3.1% Samsung 340 2.9% Renesas Electronics 279 2.4% (Consultant) 258 2.2% Texas Instruments 217 1.9% Broadcom 162 1.4% Oracle 155 1.3% Imagination Technologies 151 1.3% Cisco 150 1.3% Freescale 134 1.1% MEV Limited 129 1.1% ARM 129 1.1%

By lines changed Intel 74566 12.6% Red Hat 41496 7.0% (None) 40119 6.8% IBM 39301 6.7% (Unknown) 31558 5.3% Linaro 29588 5.0% Code Aurora Forum 23495 4.0% Samsung 22175 3.8% Google 21588 3.7% Renesas Electronics 17548 3.0% SUSE 16830 2.9% Broadcom 15202 2.6% Freescale 15156 2.6% Imagination Technologies 10935 1.9% VECTOR Institute 10742 1.8% Nokia 9829 1.7% MediaTek 9582 1.6% Texas Instruments 8843 1.5% Collabora Multimedia 8621 1.5% (Consultant) 8312 1.4%

As usual, there are few surprises here, with the possible exception of the 3.3% of the changesets contributed in this cycle by current and aspiring Outreachy interns.

The Signed-off-by tags in a patch provide a picture of who handled the patch on its way into the appropriate subsystem maintainer's tree. In particular, if one looks at tags applied by developers other than the author of each patch, the result gives a view of who the gatekeepers are. For the 4.1 development cycle, the numbers look like this:

Most non-author signoffs in 4.1
By Developer Greg Kroah-Hartman 1544 13.8% David S. Miller 1067 9.6% Ingo Molnar 407 3.6% Mark Brown 405 3.6% Andrew Morton 404 3.6% Daniel Vetter 360 3.2% Mauro Carvalho Chehab 342 3.1% Ralf Baechle 263 2.4% Arnaldo Carvalho de Melo 242 2.2% Kalle Valo 210 1.9%	By employer Red Hat 2249 20.2% Linux Foundation 1568 14.1% Intel 1327 11.9% Linaro 981 8.8% Google 621 5.6% Samsung 521 4.7% SUSE 375 3.4% (None) 316 2.8% (Unknown) 314 2.8% IBM 286 2.6%

While this development cycle is the result of the work of 1,500 developers and over 200 companies, at the subsystem maintainer level things are, as always, far more concentrated: over 60% of the changes going into this kernel passed through the hands of developers working for just five companies. This concentration reflects a simple fact: while many companies are willing to support developers working on specific tasks, the number of companies supporting subsystem maintainers is far smaller. Subsystem maintainership is also, increasingly, not a job for volunteer developers.

And that is the story for the 4.1 development cycle. The kernel-development machine continues to hum along, integrating the work of thousands of developers and producing the kernels that run Linux systems worldwide. There are not many surprises to be seen here, but, for such an important piece of software, "not many surprises" is generally deemed to be a good thing.