Statistics from the 3.9 development cycle

As of this writing, Linus has stated that 3.9-rc7 should be the last prepatch for the 3.9 development cycle. If that prediction holds, the final 3.9 release can be expected sometime around April 21, after a 62-day development cycle. That is not the shortest cycle ever, but it is getting close; in general, the community has been producing kernels more quickly in the last year, with no kernel after 3.3 taking more than 71 days. No kernel has gone past -rc8 since the release of 3.1-rc10 in October 2011 — and that was a special case caused by the kernel.org breakin. At this point, everybody seems to know how the process works, and things go pretty smoothly.

3.8 was the most active development cycle ever. At 11,746 non-merge changesets (as of this writing), 3.9 will not beat that record, but it will set one of its own: the 1,364 developers who contributed to this kernel are the most ever. The most active of those developers were:

Most active 3.9 developers

By changesets Takashi Iwai 265 2.3% H Hartley Sweeten 259 2.2% Al Viro 208 1.8% Tejun Heo 186 1.6% Johannes Berg 178 1.5% Kees Cook 177 1.5% Daniel Vetter 128 1.1% Alex Elder 119 1.0% Eric W. Biederman 109 0.9% Laurent Pinchart 109 0.9% Mark Brown 107 0.9% Yinghai Lu 98 0.8% Peter Huewe 95 0.8% Kevin McKinney 95 0.8% Vineet Gupta 94 0.8% Rafael J. Wysocki 90 0.8% Hideaki Yoshifuji 85 0.7% Jingoo Han 81 0.7% Sachin Kamat 76 0.7% Mauro Carvalho Chehab 75 0.6%

By changed lines Paul Gortmaker 34927 4.7% Laurent Pinchart 32137 4.3% James Hogan 27808 3.7% Johannes Berg 25451 3.4% Takashi Iwai 20096 2.7% Vineet Gupta 19886 2.7% Ralf Baechle 15210 2.0% Manjunath Hadli 14527 1.9% George Zhang 10154 1.4% H Hartley Sweeten 8796 1.2% Sony Chacko 8781 1.2% Ariel Elior 8590 1.1% Joe Thornber 7724 1.0% Prashant Gaikwad 7558 1.0% Al Viro 6749 0.9% Christoffer Dall 6402 0.9% Andy King 6063 0.8% Ben Skeggs 5563 0.7% Ian Minett 4943 0.7% Bob Moore 4542 0.6%

H. Hartley Sweeten continues to work on the cleanup of the Comedi drivers, but, for the first time since 3.5, he has been pushed out of the top position by Takashi Iwai, who merged a vast amount of ALSA sound driver work for 3.9. Al Viro has been working on the cleanup of a number of virtual filesystem APIs, but much of his work this time around was also focused on making the signal code more generic and architecture-independent. Tejun Heo's work is divided between improving the control group subsystem, improving workqueues, and simplifying the IDR API. Johannes Berg is highly active in wireless networking, and with the core mac80211 subsystem in particular.

Paul Gortmaker got to the top of the "lines changed" column through the removal of a number of old, obsolete network drivers; the kernel lost over 34,000 lines of code as the result of his work. Laurent Pinchart did a lot of low-level embedded architecture cleanup and improvement work, and James Hogan added the new Meta architecture.

One could look at the development statistics and conclude that the average kernel developer contributed eight or nine changesets during the 39 cycle. The truth of the matter is a little different, as can be seen in this plot:

Just over one third of the developers working on 3.9 contributed a single patch, and the median developer contributed two. Meanwhile, the 100 most active developers contributed more than half of all the patches merged in this cycle. This pattern where a relatively small group of developers is responsible for the bulk of the changes has not changed much in recent years.

219 companies (that we know of) supported development of the 3.9 kernel. The most active of these companies were:

Most active 3.9 employers

By changesets Intel 1185 10.2% (None) 1180 10.1% Red Hat 1050 9.0% (Unknown) 846 7.3% SUSE 618 5.3% Google 406 3.5% Linaro 397 3.4% Texas Instruments 367 3.1% IBM 339 2.9% Samsung 334 2.9% Vision Engraving Systems 259 2.2% NVidia 208 1.8% Renesas Electronics 203 1.7% Oracle 170 1.5% Fujitsu 161 1.4% Broadcom 157 1.3% Wolfson Microelectronics 129 1.1% Inktank Storage 128 1.1% Freescale 119 1.0% Arista Networks 109 0.9%

By lines changed Intel 75386 10.1% Renesas Electronics 66290 8.8% Wind River 50740 6.8% Red Hat 48424 6.5% (None) 38479 5.1% SUSE 38361 5.1% (Unknown) 32336 4.3% Texas Instruments 32333 4.3% Imagination Technologies 27883 3.7% NVidia 26935 3.6% Synopsys 20298 2.7% Samsung 19555 2.6% Broadcom 17755 2.4% VMWare 16332 2.2% IBM 16313 2.2% Linaro 13794 1.8% QLogic 11460 1.5% Vision Engraving Systems 10731 1.4% Google 10581 1.4% Marvell 8210 1.1%

For the first time ever, Intel finds itself at the top of the chart in both columns, displacing Red Hat and even exceeding the total of contributions from volunteers (those marked as "(None)" above); chances are, though, that if all the developers in the "unknown" category were known, they would push the volunteer group back to the top of the list. In general, the percentage of contributions from volunteers continues its slow decline. In today's job market, it seems, anybody who is able to get code into the kernel has to be fairly determined to reject job offers to remain a volunteer.

In summary, the kernel development community remains healthy and vibrant, delivering vast amounts of work to Linux users via a process that appears to run like a well-oiled machine. There are very few projects, either free or proprietary, that can sustain this kind of pace for years at a time. Given the kernel's history, it seems likely that things will continue in this vein for some time; it is going to be fun to watch.

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