Some 4.20 development statistics

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This year's holiday gifts will include the 4.20 kernel; that can only mean that it is time for another look at where the code going into this release has come from. This development cycle was typically busy and brought a lot of new code into the kernel. There are some new faces showing up in the statistics this time around, but not a lot of surprises otherwise.

As of this writing, 13,856 non-merge changesets have found their way into the mainline repository for the 4.20 release; they were contributed by 1,743 developers. That makes 4.20 the busiest cycle since 4.15, but only by a little bit; both numbers are essentially in line with recent release history. Of those 1,743 developers, 283 were first-time contributors this time around. The most active 4.20 contributors were:

Most active 4.20 developers By changesets Lorenzo Bianconi 198 1.4% Christoph Hellwig 145 1.0% Laurent Pinchart 142 1.0% Yue Haibing 141 1.0% Paul E. McKenney 138 1.0% Marcel Ziswiler 133 1.0% Matthew Wilcox 129 0.9% Rob Herring 126 0.9% Colin Ian King 125 0.9% Christian König 111 0.8% Chris Wilson 110 0.8% Hans Verkuil 109 0.8% Trond Myklebust 102 0.7% John Whitmore 101 0.7% Andy Shevchenko 97 0.7% Nathan Chancellor 91 0.7% Kuninori Morimoto 88 0.6% Linus Walleij 85 0.6% Zhong Jiang 84 0.6% Michael Straube 84 0.6% By changed lines Feifei Xu 62965 8.2% Spencer E. Olson 34216 4.5% Hannes Reinecke 21700 2.8% Guo Ren 11713 1.5% Ard Biesheuvel 11227 1.5% Matthew Wilcox 10435 1.4% Lorenzo Bianconi 10342 1.4% Anirudh Venkataramanan 8986 1.2% Evan Quan 8785 1.1% Sasha Neftin 8393 1.1% Horia Geantă 8080 1.1% David Howells 8012 1.0% Laurent Pinchart 7964 1.0% Jesse Brandeburg 7882 1.0% Sunil Goutham 7181 0.9% Boris Brezillon 6211 0.8% Hao Zheng 5852 0.8% Christoph Hellwig 5326 0.7% Hans Verkuil 5084 0.7% Greg Kroah-Hartman 4829 0.6%

Lorenzo Bianconi reached the top of the "by changesets" column with a long set of changes to the mt76 network driver. Christoph Hellwig did a bunch of work in the block subsystem, as well as some significant improvements to the DMA mapping layer. Laurent Pinchart worked mostly with graphics drivers, Yue Haibing did a lot of cleanup work in various device drivers, and Paul McKenney worked mostly in the read-copy-update subsystem.

As is often the case, the "changed lines" column was dominated by changes to the AMD graphics drivers; Feifei Xu landed at the top with 15 patches adding more header files for those drivers. Spencer Olson made a bunch of improvements to the comedi drivers in the staging subsystem, Hannes Reinecke replaced the DAC960 driver with a reimplemented version, Guo Ren added the C-SKY architecture, and Ard Biesheuvel did a bunch of core work in the crypto subsystem, the jump label mechanism, and the Arm architecture.

Reviewing and testing patches are important parts of the development process. The most active reviewers and testers this time around were:

Test and review credits in 4.20 Tested-by Andrew Bowers 155 13.9% Jacopo Mondi 38 3.4% Stefan Wahren 30 2.7% Aaron Brown 26 2.3% Arnaldo Carvalho de Melo 24 2.1% Steve Longerbeam 24 2.1% Marcel Holtmann 22 2.0% Kees Cook 18 1.6% Mathieu Malaterre 17 1.5% Catalin Marinas 16 1.4% Niklas Cassel 15 1.3% Michael Schmitz 15 1.3% Mathieu Poirier 15 1.3% Sedat Dilek 15 1.3% Tony Brelinski 15 1.3% Tony Lindgren 14 1.3% Jarkko Nikula 14 1.3% Hiroyuki Yokoyama 14 1.3% Jeremy Linton 13 1.2% Farhan Ali 13 1.2% Reviewed-by Rob Herring 190 3.7% Alex Deucher 150 2.9% Simon Horman 148 2.9% Sebastian Reichel 109 2.1% Christoph Hellwig 107 2.1% Geert Uytterhoeven 92 1.8% Huang Rui 91 1.8% Andrew Morton 75 1.5% David Sterba 74 1.4% Chao Yu 61 1.2% Laurent Pinchart 56 1.1% Christian König 54 1.1% Biju Das 50 1.0% Junwei Zhang 49 1.0% Thomas Gleixner 48 0.9% Bjorn Andersson 47 0.9% Felix Kuehling 46 0.9% Nick Desaulniers 46 0.9% Fabrizio Castro 46 0.9% Johannes Thumshirn 45 0.9%

Of the nearly 14,000 changes in 4.20, 953 (just under 7%) had Tested-by tags, while 4,198 (30%) had Reviewed-by tags.

Work on 4.20 was supported by 223 companies that we know of; the most active of those companies were:

Most active 4.20 employers By changesets Intel 1328 9.6% Red Hat 1170 8.4% (None) 962 6.9% (Unknown) 764 5.5% Linaro 647 4.7% AMD 645 4.7% IBM 627 4.5% Huawei Technologies 494 3.6% Google 484 3.5% Renesas Electronics 449 3.2% (Consultant) 370 2.7% Mellanox 360 2.6% SUSE 328 2.4% Oracle 256 1.8% ARM 254 1.8% Bootlin 216 1.6% Code Aurora Forum 204 1.5% NXP Semiconductors 180 1.3% Cisco 174 1.3% Canonical 152 1.1% By lines changed AMD 94015 12.3% Intel 84990 11.1% (Unknown) 57939 7.6% Red Hat 53010 6.9% Code Aurora Forum 30456 4.0% (None) 29797 3.9% SUSE 29573 3.9% IBM 28748 3.8% Linaro 28460 3.7% Bootlin 17824 2.3% (Consultant) 16557 2.2% Marvell 15781 2.1% NXP Semiconductors 13893 1.8% MediaTek 13599 1.8% Mellanox 13555 1.8% Renesas Electronics 13486 1.8% Google 12684 1.7% Hangzhou C-SKY Microsystems 11713 1.5% Huawei Technologies 11041 1.4% Microsoft 9020 1.2%

As usual, there are few surprises here; while many companies contribute to the kernel, the list of those doing the most work tends to be restricted to a fairly small number of them. It is worth noting that, of the 283 first-time contributors seen during this development cycle, 17 were working at Intel as of their first commit, while 13 were at the Code Aurora Forum, 12 at AMD, and 10 at Google. All told, over half of the first-time contributors were already affiliated with a company.

If one looks only at the 1,339 patches touching core kernel code (loosely defined as the contents of the fs , kernel , and mm directory trees), the results come out a bit different:

Most active core-kernel contributors Developers Paul E. McKenney 125 9.3% Matthew Wilcox 72 5.4% Darrick J. Wong 36 2.7% Chao Yu 34 2.5% David Howells 32 2.4% Christoph Hellwig 31 2.3% Steve French 28 2.1% Trond Myklebust 26 1.9% Miklos Szeredi 25 1.9% Eric W. Biederman 23 1.7% Companies Red Hat 218 16.3% IBM 148 11.1% SUSE 112 8.4% Microsoft 89 6.6% Huawei Technologies 73 5.5% (Unknown) 71 5.3% Oracle 69 5.2% Linaro 57 4.3% Facebook 41 3.1% Google 40 3.0%

There are a lot of companies that find it in their interest to support work on the Linux kernel, but rather fewer of them put resources into the core code that everybody uses.

Contributions all over the kernel tree are the fuel that keeps this project going, though. Once again, it would appear that, despite whatever problems the community may have, the kernel-development machine continues to run smoothly, integrating vast amounts of work into a new release every nine or ten weeks.

