Statistics for the 4.15 kernel

The 4.15 kernel is likely to require a relatively long development cycle as a result of the post-rc5 merge of the kernel page-table isolation patches. That said, it should be in something close to its final form, modulo some inevitable bug fixes. The development statistics for this kernel release look fairly normal, but they do reveal an unexpectedly busy cycle overall.

This development cycle was supposed to be relatively calm after the anticipated rush to get work into the 4.14 long-term-support release. But, while 4.14 ended up with 13,452 non-merge changesets at release, 4.15-rc6 already has 14,226, making it one of the busiest releases in the kernel project's history. Only 4.9 (16,214 changesets) and 4.12 (14,570) brought in more work, and 4.15 may exceed 4.12 by the time it is finished. So far, 1,707 developers have contributed to this kernel; they added 725,000 lines of code while removing 407,000, for a net growth of 318,000 lines of code.

The most active developers this time around were:

Most active 4.15 developers

By changesets Kees Cook 349 2.5% Colin Ian King 237 1.7% Harry Wentland 170 1.2% Ben Skeggs 156 1.1% Gustavo A. R. Silva 138 1.0% Christoph Hellwig 137 1.0% Geert Uytterhoeven 136 1.0% Arnd Bergmann 134 0.9% Chris Wilson 129 0.9% Dmytro Laktyushkin 125 0.9% Allen Pais 112 0.8% Masahiro Yamada 108 0.8% Thomas Gleixner 105 0.7% Dave Airlie 103 0.7% Eric Dumazet 99 0.7% Ville Syrjälä 97 0.7% Arvind Yadav 95 0.7% Jakub Kicinski 94 0.7% Markus Elfring 92 0.6% Mauro Carvalho Chehab 89 0.6%

By changed lines Harry Wentland 152262 16.8% Dave Airlie 47651 5.2% Takashi Iwai 41943 4.6% Dmytro Laktyushkin 28306 3.1% Rex Zhu 24008 2.6% Andy Shevchenko 18204 2.0% Paul E. McKenney 14629 1.6% Ben Skeggs 12684 1.4% Palmer Dabbelt 10433 1.1% David Howells 10210 1.1% Darrick J. Wong 8792 1.0% Yue Hin Lau 8483 0.9% Greg Kroah-Hartman 8298 0.9% Kees Cook 7091 0.8% Christoph Hellwig 7076 0.8% Linus Walleij 6757 0.7% Jakub Kicinski 6402 0.7% Wei Hu 5967 0.7% Mauro Carvalho Chehab 5692 0.6% Alex Deucher 5406 0.6%

Kees Cook was this cycle's most prolific contributor of changesets; he did security-related work throughout the kernel, but the bulk of the patches implemented the internal kernel-timer API change. Colin Ian King contributed cleanup patches all over the kernel, Harry Wentland added another massive pile of AMD graphics driver code, Ben Skeggs worked on the Nouveau driver as usual, and Gustavo Silva focused on marking fall-through cases in switch statements (as in this patch).

In the lines-changed column, Wentland's AMD graphics driver additions topped the list. Dave Airlie brought the AMD display core code into the graphics subsystem, but also did a bunch of cleanup work resulting in the removal of over 21,000 lines of code. Takashi Iwai worked all over the audio subsystem; in particular, he removed the ancient Open Sound System code, shrinking the kernel by over 40,000 lines. Dmytro Laktyushkin and Rex Zhu also added more AMD graphics code. The AMD graphics drivers thus dominated the changes in this cycle in terms of lines of code, as has been the case for a number of recent development cycles.

It is worth noting once again that staging-tree work hardly figures in these numbers at all; the days when staging was the biggest driver of kernel changes appear to be done. The page-table isolation work also doesn't show up much here either, showing that important changes often come in relatively small packages.

The work in 4.15 was supported by 231 companies (that we can identify), more than worked on 4.14 but still a relatively small number by recent standards; 4.10 remains the record holder with 271 companies participating. The most active companies this time around were:

Most active 4.15 employers

By changesets Intel 1609 11.3% AMD 1526 10.7% Red Hat 955 6.7% (None) 813 5.7% Google 739 5.2% (Unknown) 703 4.9% Linaro 489 3.4% IBM 450 3.2% Oracle 390 2.7% Renesas Electronics 343 2.4% Mellanox 340 2.4% Linux Foundation 307 2.2% ARM 306 2.2% SUSE 294 2.1% Broadcom 260 1.8% Huawei Technologies 257 1.8% Canonical 254 1.8% (Consultant) 251 1.8% Samsung 221 1.6% Netronome Systems 157 1.1%

By lines changed AMD 266230 29.3% Red Hat 97177 10.7% Intel 82791 9.1% SUSE 46479 5.1% (Unknown) 33739 3.7% IBM 33105 3.6% (None) 24842 2.7% Linaro 23291 2.6% Google 17760 2.0% Broadcom 15482 1.7% Mellanox 14923 1.6% Samsung 13841 1.5% Oracle 13755 1.5% Huawei Technologies 13655 1.5% ARM 13118 1.4% Renesas Electronics 10762 1.2% Netronome Systems 10366 1.1% Linux Foundation 9855 1.1% ST Microelectronics 8803 1.0% Chelsio 8695 1.0%

The AMD graphics work shows clearly in these numbers; otherwise, the results are typical for recent development cycles.

The Signed-off-by tags attached to patches give clues as to who took responsibility for their development. In particular, if one looks at the signoffs attached by developers other than the author of the patch, the result is a picture of who accepted the patches for merging into the mainline — the most active maintainers, in other words. For the 4.15 kernel, the results look like this:

Non-author signoffs in 4.15

By developer David S. Miller 1942 14.1% Alex Deucher 1551 11.3% Greg Kroah-Hartman 749 5.5% Ingo Molnar 397 2.9% Mark Brown 329 2.4% Doug Ledford 300 2.2% Mauro Carvalho Chehab 287 2.1% Andrew Morton 271 2.0% Jens Axboe 240 1.7% Martin K. Petersen 226 1.6% Thomas Gleixner 218 1.6% Simon Horman 177 1.3% Herbert Xu 174 1.3% Jeff Kirsher 156 1.1% Kalle Valo 152 1.1% Michael Ellerman 151 1.1% Jiri Pirko 126 0.9% David Sterba 114 0.8% Martin Schwidefsky 113 0.8% Linus Walleij 110 0.8%

By company Red Hat 3334 24.3% AMD 1681 12.2% Intel 1088 7.9% Linaro 904 6.6% Linux Foundation 769 5.6% Google 479 3.5% Samsung 440 3.2% Oracle 395 2.9% IBM 372 2.7% Facebook 334 2.4% Huawei Technologies 328 2.4% (None) 320 2.3% Mellanox 283 2.1% SUSE 270 2.0% Renesas Electronics 219 1.6% Free Electrons 218 1.6% Linutronix 218 1.6% Code Aurora Forum 214 1.6% (Consultant) 181 1.3% ARM 176 1.3%

Kernel subsystem maintainers have long been concentrated in a relatively small set of companies. That situation is slowly changing, but it's still true that, in 4.15, half of the changes merged were accepted by developers working for just four companies.

Finally, the most active bug reporters and patch testers, according to the Reported-by and Tested-by tags attached to patches, were:

Bug reporters and testers in 4.15
Reported-by credits kernel test robot 36 5.5% Dan Carpenter 25 3.8% syzbot 25 3.8% Dmitry Vyukov 12 1.8% Andrey Konovalov 11 1.7% Geert Uytterhoeven 9 1.4% Arnd Bergmann 7 1.1% Michael Ellerman 7 1.1% Randy Dunlap 7 1.1% Brian Foster 7 1.1% Stephen Rothwell 7 1.1% Jianlin Shi 7 1.1% Jakub Kicinski 6 0.9%	Tested-by credits Andrew Bowers 114 12.7% Juergen Gross 52 5.8% Yu Chen 51 5.7% Krishneil Singh 22 2.4% Borislav Petkov 20 2.2% Oleksandr Natalenko 16 1.8% Arnaldo Carvalho de Melo 15 1.7% Aaron Brown 13 1.4% Sean Wang 12 1.3% Chris Brandt 12 1.3% Xin Long 11 1.2% Geert Uytterhoeven 9 1.0% Lee Tibbert 9 1.0%

A relatively new entry here is "syzbot", which is an operation run by Dmitry Vyukov at Google. Syzbot runs the syzkaller fuzz tester in an automated mode and reports the (numerous) crashes that result. As can be seen in the tags, those reports are leading to a steady stream of bug fixes, which can only be a good thing.

The story told by that final table is incomplete, though, in that most bug reporting and (especially) most testing goes untracked. The kernel community counts on many people beyond those who directly contribute code; it will never be possible to credit them all. As a whole, this community remains large, active, and growing, and the first kernel to be released in 2018 will reflect that.

Index entries for this article
Kernel	Releases/4.15

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