Developer statistics for 2.6.30

Once again, 2.6.30 was a large development cycle; it saw the incorporation (through just after 2.6.30-rc7) of 11,733 non-merge changesets from 1125 developers. The number of changesets exceeds 2.6.29, but the number of developers falls just short of the 1166 seen last time around. Those developers added 1.14 million lines of code this time around, while taking out 513,000, for a net growth of 624,000 lines.

The individual developer statistics for 2.6.30 look like:

Most active 2.6.30 developers

By changesets Ingo Molnar 324 2.8% Bill Pemberton 227 1.9% Stephen Hemminger 204 1.7% Hans Verkuil 199 1.7% Takashi Iwai 188 1.6% Bartlomiej Zolnierkiewicz 186 1.6% Steven Rostedt 179 1.5% Greg Kroah-Hartman 150 1.3% Jeremy Fitzhardinge 125 1.1% Mark Brown 107 0.9% Jaswinder Singh Rajput 105 0.9% Rusty Russell 100 0.9% Tejun Heo 98 0.8% Johannes Berg 98 0.8% Hannes Eder 88 0.8% Michal Simek 85 0.7% Luis R. Rodriguez 85 0.7% Sujith 85 0.7% David Howells 80 0.7% Yinghai Lu 78 0.7%

By changed lines Greg Kroah-Hartman 120353 9.0% ADDI-DATA GmbH 43420 3.3% Mithlesh Thukral 42424 3.2% Alex Deucher 26576 2.0% David Schleef 25905 1.9% David Woodhouse 24636 1.8% Ramkrishna Vepa 23495 1.8% Lior Dotan 22506 1.7% Eric Moore 22266 1.7% Eilon Greenstein 18399 1.4% Jaswinder Singh Rajput 18168 1.4% Hans Verkuil 18048 1.4% David Howells 17941 1.3% Andy Grover 16355 1.2% Michal Simek 15827 1.2% Sri Deevi 15514 1.2% Frank Mori Hess 15450 1.2% Ben Hutchings 15031 1.1% Ingo Molnar 13876 1.0% Bill Pemberton 13817 1.0%

On the changesets side, Ingo Molnar is at the top of the list this time around; as usual, he created a vast number of patches - about five per day - in the x86 architecture code, ftrace, and beyond. Bill Pemberton is perhaps better known as the maintainer of the Elm mail client; he did a lot of cleanup work with the COMEDI drivers in the -staging tree. The bulk of Stephen Hemminger's work involved converting network drivers to the new net_device_ops API. Hans Verkuil continues to improve the Video4Linux2 framework and associated drivers, and Takashi Iwai continues to generate a lot of patches as the ALSA maintainer.

Linus kicked off the 2.6.30 development cycle by noting that about one third of the changes in 2.6.30-rc1 were "crap." So, unsurprisingly, the top three entries in the "by changed lines" column all got there through the addition of -staging drivers. Alex Deucher added Radeon R6xx/R7xx support; many of his "changed lines" were associated microcode firmware. And David Schleef added another set of drivers to the -staging tree.

Contributions to 2.6.30 could be traced back to some 190 employers. Looking at the most-active employer information, we see:

Most active 2.6.30 employers

By changesets (None) 1970 16.8% Red Hat 1305 11.1% (Unknown) 1184 10.1% Intel 855 7.3% Novell 832 7.1% IBM 630 5.4% (Consultant) 293 2.5% Atheros Communications 262 2.2% Oracle 252 2.1% University of Virginia 227 1.9% Fujitsu 217 1.8% Vyatta 204 1.7% Renesas Technology 152 1.3% NTT 121 1.0% MontaVista 115 1.0% HP 107 0.9% Wolfson Microelectronics 105 0.9% (Academia) 102 0.9% Nokia 98 0.8% XenSource 91 0.8%

By lines changed (Unknown) 181413 13.6% Novell 164229 12.3% (None) 118095 8.9% Intel 86060 6.5% Red Hat 73954 5.5% LinSysSoft Technologies 64798 4.9% ADDI-DATA GmbH 43420 3.3% SofaWare 39245 2.9% Broadcom 31956 2.4% AMD 28364 2.1% Entropy Wave 25905 1.9% IBM 25702 1.9% Oracle 25588 1.9% NTT 25235 1.9% Neterion 23495 1.8% LSI Logic 22304 1.7% Atheros Communications 21627 1.6% (Consultant) 19209 1.4% Freescale 16139 1.2% PetaLogix 15846 1.2%

These numbers are somewhat similar to those seen in previous development cycles. There are a few unfamiliar companies here; they are pretty much all present as a result of contributions to -staging. It is interesting to note that Atheros and Broadcom, once known as uncooperative companies, are increasing their contributions over time.

Your editor has not looked at signoff statistics for the last few cycles. The interesting thing to be found in Signed-off-by tags is an indication of who the gatekeepers to the kernel are. Especially if one disregards signoffs by the author of each patch, what remains is (mostly) the signoffs of subsystem maintainers who approved the patches for merging. For 2.6.30, these numbers look like this:

Top non-author signoffs in 2.6.30

Individuals David S. Miller 1216 12.1% John W. Linville 865 8.6% Ingo Molnar 836 8.3% Greg Kroah-Hartman 797 7.9% Mauro Carvalho Chehab 784 7.8% Andrew Morton 660 6.6% James Bottomley 250 2.5% Linus Torvalds 219 2.2% Len Brown 189 1.9% Takashi Iwai 165 1.6% Jeff Kirsher 145 1.4% Russell King 127 1.3% H. Peter Anvin 120 1.2% Mark Brown 115 1.1% Jesse Barnes 111 1.1% Benjamin Herrenschmidt 111 1.1% Reinette Chatre 104 1.0% Martin Schwidefsky 95 0.9% Avi Kivity 91 0.9% Paul Mundt 89 0.9%

Employers Red Hat 4264 42.4% Novell 1386 13.8% Intel 951 9.5% Google 660 6.6% (None) 408 4.1% IBM 378 3.8% Linux Foundation 219 2.2% (Consultant) 166 1.6% (Unknown) 127 1.3% Wolfson Microelectronics 115 1.1% Renesas Technology 92 0.9% Marvell 91 0.9% Atomide 81 0.8% Oracle 80 0.8% Astaro 65 0.6% Freescale 63 0.6% Cisco 61 0.6% Analog Devices 60 0.6% Univ. of Michigan CITI 59 0.6% Panasas 58 0.6%

Signoffs have always been more concentrated than contributions in general. Still, one wonders how David Miller manages to approve a solid twenty patches every day. On the employer side, things are more concentrated than ever; over half of the patches going into the kernel go through the hands of a developer at Red Hat or Novell. Developers, it seems, work for a great many companies, but subsystem maintainers gravitate toward a small handful of firms.

All told, the picture remains one of a well-oiled, fast-moving development process. We also see a picture of a -staging tree which is growing at a tremendous rate; your editor is tempted to exclude -staging patches from future reports if the rate does not slow somewhat. Even without -staging, though, a lot of work is being done on the kernel, with the participation of a large group of developers, and it doesn't look like it will be slowing down anytime soon.

Postscript: Jan Engelhardt sent your editor a pointer to a short script which, through use of the git blame command, tallies up the "ownership" of every line in the kernel. The top results for 2.6.30-rc7 look like this:

Who last touched kernel code lines
Lines	Pct	Who
4063723	35.17%	Linus Torvalds
464021	4.02%	Greg Kroah-Hartman
94200	0.82%	David Howells
86031	0.74%	David S. Miller
82608	0.71%	Luis R. Rodriguez
72200	0.62%	Bryan Wu
70128	0.61%	Takashi Iwai
66859	0.58%	Ralf Baechle
55785	0.48%	Hans Verkuil
54069	0.47%	Paul Mundt
54007	0.47%	Kumar Gala
53288	0.46%	David Brownell
51640	0.45%	Russell King
50611	0.44%	Paul Mackerras
49499	0.43%	Andrew Victor
49347	0.43%	Mauro Carvalho Chehab
49256	0.43%	Alan Cox
47305	0.41%	Mikael Starvik
47040	0.41%	Ben Dooks
44307	0.38%	Benjamin Herrenschmidt

Linus shows a high ownership because he was the initial committer at the beginning of the git era. To a rough approximation, one can conclude that approximately one third of the code in the kernel has not been touched since that time. There are other interesting things which can be done with line-level statistics; your editor plans to explore this idea some in the future.