Who wrote - and approved - 2.6.22

As of this writing, just over 6,000 changesets have been accepted for 2.6.22. Those patches were contributed by 885 different developers, added 494,000 lines, and deleted 241,000 other lines (without counting renames, which would otherwise increase both numbers by about 60,000 lines). That makes 2.6.22 a large change relative to its immediate predecessors:

Release	Developers	Changesets	Lines added	Lines removed
2.6.20	741	4983	286,000	160,000
2.6.21	842	5349	343,000	199,000
2.6.22-rc4+	885	6093	494,000	241,000

Here's the top contributors of those changes:

Most active 2.6.22 developers

By changesets David S. Miller 175 3.0% Kristian Høgsberg 109 1.9% Stephen Hemminger 86 1.5% Arnaldo Carvalho de Melo 82 1.4% Andrew Morton 79 1.3% Stefan Richter 79 1.3% Christoph Lameter 77 1.3% Patrick McHardy 76 1.3% Jean Delvare 75 1.3% Dmitry Torokhov 70 1.2% Stephen Rothwell 68 1.2% Paul Mundt 66 1.1% David Brownell 65 1.1% Jeff Dike 63 1.1% Alan Cox 60 1.0% Andi Kleen 59 1.0% Antonino Daplas 58 1.0% Adrian Bunk 58 1.0% Tejun Heo 57 1.0% Russell King 57 1.0%

By changed lines Bryan Wu 77594 12.9% David Howells 23310 3.9% Marcelo Tosatti 22351 3.7% Patrick McHardy 21746 3.6% Jiri Benc 18328 3.0% Hans Verkuil 13683 2.3% David S. Miller 13595 2.3% Roland Dreier 12247 2.0% Artem B. Bityutskiy 12065 2.0% Kristian Høgsberg 11153 1.9% Robert P. J. Day 7554 1.3% Christoph Lameter 7378 1.2% Andrew Victor 6638 1.1% Mike Frysinger 6313 1.0% David Brownell 6033 1.0% Michael Chan 5851 1.0% Andi Kleen 5431 0.9% David Gibson 5321 0.9% Nobuhiro Iwamatsu 5296 0.9% Mark Fasheh 4921 0.8%

Bryan Wu makes it to the top of the list of contributors (by lines changed) by virtue of being the person to contribute support for the Blackfin architecture. David Howells contributed the AF_RXRPC and AFS filesystem work; Marcelo Tosatti wrote the OLPC "Libertas" wireless driver, and Jiri Benc's name appears on the mac80211 stack.

When broken down by employer, the (approximate, as always) numbers come out like this:

Most active 2.6.22 employers

By changesets (Unknown) 1766 30.2% Red Hat 720 12.3% IBM 601 10.3% Novell 411 7.0% (None) 245 4.2% Intel 203 3.5% Oracle 127 2.2% (Consultant) 119 2.0% Linux Foundation 116 2.0% Google 111 1.9% SGI 93 1.6% Nokia 83 1.4% Freescale 80 1.4% Astaro 76 1.3% XenSource 56 1.0% MontaVista 56 1.0% Qumranet 55 0.9% HP 53 0.9% QLogic 52 0.9% Analog Devices 49 0.8%

By lines changed (Unknown) 130164 21.6% Red Hat 104627 17.4% Analog Devices 84561 14.0% Novell 41366 6.9% IBM 33629 5.6% Astaro 22065 3.7% (None) 20097 3.3% (Consultant) 15403 2.6% Linutronix 13585 2.3% Intel 12288 2.0% Cisco 12280 2.0% Oracle 10482 1.7% Freescale 10116 1.7% SGI 8639 1.4% Nokia 7328 1.2% SANPeople 7045 1.2% Broadcom 5952 1.0% MontaVista 5810 1.0% Linux Foundation 5746 1.0% Atmel 5220 0.9%

One thing which jumps out here is that the amount of code contributed by developers known to be working on their own time has dropped; 2.6.22 will be one of the most corporate kernels yet.

Looking at the developers who put Signed-off-by lines onto patches yields some interesting results. If one tabulates all 12,678 signoffs in 2.6.22, the results look like this:

Developers with the most signoffs (total 12678)
Andrew Morton	1415	11.2%
Linus Torvalds	1299	10.2%
David S. Miller	814	6.4%
Paul Mackerras	381	3.0%
Jeff Garzik	344	2.7%
Andi Kleen	252	2.0%
Greg Kroah-Hartman	236	1.9%
Mauro Carvalho Chehab	236	1.9%
Stefan Richter	210	1.7%
Russell King	189	1.5%
James Bottomley	176	1.4%
Jaroslav Kysela	145	1.1%
Takashi Iwai	131	1.0%
Len Brown	126	1.0%
Kristian Høgsberg	126	1.0%
Patrick McHardy	117	0.9%
Jean Delvare	110	0.9%
Roland Dreier	109	0.9%
Antonino Daplas	106	0.8%
Dmitry Torokhov	105	0.8%

All authors must sign off on their code. Additionally, any maintainer who passes a patch up toward the mainline adds a signoff indicating that he or she believes the code is legitimate and suitable for inclusion. If one excludes signoffs by the author of each patch, the remaining 7,000 signoffs are (almost) all by people through whom the code has passed (a few of them are by additional authors of the patch). Those adding non-author signoffs can thus be thought of as the gatekeepers through whom each patch must pass. Non-author signoffs break down like this:

Non-author signoffs (total 7028)
Andrew Morton	1336	19.0%
Linus Torvalds	1279	18.2%
David S. Miller	640	9.1%
Paul Mackerras	371	5.3%
Jeff Garzik	322	4.6%
Greg Kroah-Hartman	222	3.2%
Mauro Carvalho Chehab	216	3.1%
Andi Kleen	193	2.7%
James Bottomley	163	2.3%
Jaroslav Kysela	142	2.0%
Russell King	132	1.9%
Stefan Richter	131	1.9%
Len Brown	115	1.6%
John W. Linville	85	1.2%
Roland Dreier	85	1.2%
Takashi Iwai	79	1.1%
Martin Schwidefsky	54	0.8%
David Woodhouse	53	0.8%
Ralf Baechle	48	0.7%
Antonino Daplas	48	0.7%

In summary, 80% of the patches merged into the mainline kernel passed through the twenty developers listed above. One can take another step, and look at the number of non-author signoffs by employer:

Non-author signoffs by employer
Google	1338	19.0%
Linux Foundation	1281	18.2%
Red Hat	1246	17.7%
Novell	700	10.0%
(Unknown)	660	9.4%
IBM	553	7.9%
(None)	293	4.2%
Intel	193	2.7%
SteelEye	163	2.3%
Cisco	85	1.2%
MIPS Technologies	48	0.7%
Nokia	42	0.6%
Astaro	41	0.6%
Analog Devices	35	0.5%
QLogic	35	0.5%
Cendio	32	0.5%
SGI	28	0.4%
NetApp	28	0.4%
(Consultant)	23	0.3%
Oracle	22	0.3%

The bottom line: while Linux kernel development is a highly distributed activity, the work of several hundred developers is channeled through a surprisingly small number of individuals, and an even smaller number of companies on its way into the mainline.