4.11 Kernel development statistics

Linus Torvalds recently let it be known that the 4.11-rc7 kernel prepatch had a good chance of being the last for this development series. So the time has come to look at this development cycle and the contributors who made it happen.

As of this writing, 12,546 non-merge changesets have been pulled into the mainline repository for 4.11, making this cycle more-or-less average for recent kernels. Those changesets were contributed by 1,723 developers and grew the kernel by nearly 300,000 lines. Note that the current record for the most developers participating is 1,729 for 4.9; if another half-dozen developers put in a fix for 4.11, that record could yet fall. Of the developers contributing to 4.11, 278 made their first contribution ever in this cycle.

The most active developers in the 4.11 cycle were:

Most active 4.11 developers

By changesets Chris Wilson 226 1.8% Arnd Bergmann 160 1.3% Ingo Molnar 158 1.3% Christoph Hellwig 115 0.9% Takashi Iwai 110 0.9% Guenter Roeck 101 0.8% Bart Van Assche 94 0.7% Bhumika Goyal 89 0.7% Geert Uytterhoeven 87 0.7% Ville Syrjälä 86 0.7% James Hogan 83 0.7% Johan Hovold 80 0.6% Nikolay Borisov 79 0.6% Andy Shevchenko 77 0.6% Colin Ian King 77 0.6% Laurent Pinchart 75 0.6% Julia Lawall 74 0.6% Florian Fainelli 72 0.6% Eric Dumazet 71 0.6% Daniel Vetter 70 0.6%

By changed lines James Smart 14288 2.2% Ard Biesheuvel 14215 2.2% Selvin Xavier 13393 2.1% Greg Kroah-Hartman 11705 1.8% David VomLehn 11085 1.7% Rob Rice 9539 1.5% Eric Anholt 9460 1.5% Jakub Kicinski 9024 1.4% Chris Wilson 8986 1.4% Chad Dupuis 8829 1.4% Ingo Molnar 7753 1.2% Balbir Singh 7451 1.1% Maxime Ripard 7110 1.1% Ursula Braun 6666 1.0% Christoph Hellwig 5740 0.9% Rex Zhu 5719 0.9% Paul E. McKenney 5497 0.8% Jiri Pirko 5407 0.8% Quinn Tran 5331 0.8% Takashi Iwai 4892 0.8%

In the "by changesets" column, Chris Wilson ended up on top with a body of work mostly focused on the Intel i915 driver. Arnd Bergmann continues to apply fixes all over the tree, Ingo Molnar (primarily) contributed a massive reworking of the sched.h header file, Christoph Hellwig did significant work all over the block I/O subsystem, and Takashi Iwai added many patches as part of his role as maintainer of the audio subsystem.

In the "by changed lines" column, James Smart did a lot of work on the lpfc SCSI driver. Ard Biesheuvel's work was mostly in optimized crypto algorithms for the ARM architecture, Selvin Xavier contributed three patches adding the "bnxt_re" RDMA-over-converged-Ethernet driver, Greg Kroah-Hartman deleted some unwanted staging code, and David VomLehn added the AQtion network driver.

The developers contributing to 4.11 were supported by at least 225 employers, the most active of which were:

Most active 4.11 employers

By changesets Intel 1608 12.8% (Unknown) 1071 8.5% Red Hat 955 7.6% (None) 798 6.4% Linaro 624 5.0% IBM 493 3.9% SUSE 482 3.8% Google 375 3.0% (Consultant) 349 2.8% Samsung 303 2.4% Broadcom 296 2.4% Mellanox 269 2.1% Oracle 231 1.8% AMD 207 1.6% Renesas Electronics 197 1.6% Huawei Technologies 197 1.6% Facebook 187 1.5% Imagination Technologies 160 1.3% Canonical 156 1.2% Code Aurora Forum 146 1.2%

By lines changed Intel 80069 12.3% Broadcom 48163 7.4% (Unknown) 44046 6.8% (None) 43311 6.6% Linaro 37531 5.8% IBM 33286 5.1% Red Hat 31955 4.9% Cavium 28312 4.3% (Consultant) 24974 3.8% SUSE 15020 2.3% ST Microelectronics 14709 2.3% Mellanox 14474 2.2% Google 12185 1.9% Linux Foundation 11789 1.8% AMD 11397 1.7% Samsung 10845 1.7% Free Electrons 10258 1.6% Code Aurora Forum 9455 1.5% Netronome Systems 9172 1.4% Facebook 9023 1.4%

This table has gotten pretty boring over the years; it tends not to change much from one cycle to the next.

Developing code is important, but so are reviewing, testing, and reporting bugs. The kernel process has long had the mechanisms to track these contributions, though they are not as heavily used as they could be. The Reviewed-by tag records a reviewer's contribution explicitly; the reviewers most credited in this way in 4.11 were:

Top reviewers in 4.11
Hannes Reinecke	126
Joonas Lahtinen	125
Alex Deucher	106
Christoph Hellwig	106
Chris Wilson	92
Johannes Thumshirn	77
Geert Uytterhoeven	68
Andreas Dilger	68
Christian König	63
Tvrtko Ursulin	60
Daniel Vetter	57
Tomas Henzl	56
Andy Shevchenko	55
Laurent Pinchart	50
Oleg Drokin	50
Doug Oucharek	46
Linus Walleij	45
Liu Bo	42
Greg Kroah-Hartman	38
Darrick J. Wong	38
Chao Yu	38
Josh Triplett	37

Hannes Reinecke's review work was focused on the SCSI subsystem, while Joonas Lahtinen reviewed i915 patches. Each of them managed to review 1% of the total patch flow going into the 4.11 kernel — two patches per day for (what will probably be) a 63-day development cycle.

Of the 12,546 changesets merged for 4.11, 3,099 contained Reviewed-by tags. Needless to say, those tags do not document all of the review work that happened during this development cycle. Much review activity does not result in the addition of a tag of any type. When patches are reviewed by the subsystem maintainer that ultimately applies them, the result is usually a Signed-off-by tag instead. If one looks at those tags when applied by developers who were not the author of the patch, the result is this:

Top non-author signoffs in 4.11
David S. Miller	1473	12.4%
Greg Kroah-Hartman	961	8.1%
Andrew Morton	408	3.4%
Mark Brown	313	2.6%
Martin K. Petersen	308	2.6%
Ingo Molnar	272	2.3%
Kalle Valo	241	2.0%
Mauro Carvalho Chehab	231	1.9%
Doug Ledford	207	1.7%
Jens Axboe	203	1.7%
Michael Ellerman	187	1.6%
Linus Walleij	172	1.4%
Herbert Xu	166	1.4%
Alex Deucher	164	1.4%
Daniel Vetter	152	1.3%
Jonathan Cameron	129	1.1%
Rafael J. Wysocki	129	1.1%
David Sterba	127	1.1%
Ralf Baechle	126	1.1%
Ulf Hansson	124	1.0%

Here, it is hard to separate review activity from the overall level of activity in the relevant subsystems. But a rough correlation will certainly exist, meaning that the developers above are looking at a huge number of patches. This work often goes unsung, but it is a crucial part of the kernel development process; without it, the process would not run as smoothly or as quickly as it does now.

Testing and bug reporting can also be tracked by tags in the associated patches. Looking at those tags for 4.11 yields this table:

Testing and bug reporting in 4.11

Reported-by tags Dmitry Vyukov 47 6.9% Dan Carpenter 47 6.9% kbuild test robot 31 4.5% Greg Kroah-Hartman 12 1.8% Andrey Konovalov 10 1.5% Al Viro 9 1.3% Colin Ian King 9 1.3% Ben Hutchings 7 1.0% Bart Van Assche 7 1.0% Jay Vana 7 1.0% Russell King 6 0.9% Marc Dionne 6 0.9% Linus Torvalds 6 0.9% David Binderman 6 0.9% Geert Uytterhoeven 5 0.7% Mike Galbraith 5 0.7% Dave Jones 5 0.7% Ville Syrjälä 4 0.6% Dexuan Cui 4 0.6% Anton Blanchard 4 0.6%

Tested-by tags Andrew Bowers 70 10.0% Tomasz Nowicki 17 2.4% Bharat Bhushan 15 2.2% Arnaldo Carvalho de Melo 14 2.0% Krishneil Singh 14 2.0% Larry Finger 13 1.9% Mark Rutland 12 1.7% Florian Vaussard 10 1.4% Stan Johnson 10 1.4% Aaron Brown 10 1.4% David Lechner 9 1.3% Omar Sandoval 8 1.1% Jarkko Sakkinen 8 1.1% Xiaolong Ye 8 1.1% Jeremy McNicoll 8 1.1% Neil Armstrong 8 1.1% Geert Uytterhoeven 7 1.0% Stefan Wahren 7 1.0% Y.C. Chen 7 1.0% Laurent Pinchart 6 0.9%

Again, most of the activity out there does not result in explicit tags, especially when it comes to testing — many testers will say nothing if they do not run into problems. Regardless of whether testing and reporting are credited or not, they are critical to our ability to deliver a solid kernel over a nine or ten-week development cycle.

Index entries for this article
Kernel	Releases/4.11

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