Who wrote 2.6.23

While the 2.6.23 development cycle has not yet run its course, things are getting close enough to the end that it makes sense to start looking at the overall statistics for this release. As of this writing (shortly after 2.6.23-rc6 came out), just over 6,200 non-merge changesets had been added to the mainline kernel repository. These changesets came from 854 developers - a slightly smaller number than we saw for 2.6.22. Just over 350 of those developers contributed one single changeset.

All told, the patches added almost 430,000 lines, but also removed 406,000 lines, meaning that the kernel grew by just under 23,000 lines - a relatively small number. That is partially a result of kernel hatcheteer Adrian Bunk's work: he removed the old SpeedStep code, a number of Open Sound System drivers, Rise CPU support, and more - a total of almost 73,000 lines removed. Jeff Garzik hacked out over 41,000 lines of network driver code, and Jens Axboe got rid of over 25,000 lines of code, mostly in the form of ancient CDROM drivers.

Here is the list of the top contributors to 2.6.23, as counted by changesets merged and by lines of code changed:

Most active 2.6.23 developers

By changesets Ingo Molnar 152 2.5% Ralf Baechle 119 1.9% Trond Myklebust 116 1.9% Paul Mundt 111 1.8% David S. Miller 107 1.7% Tejun Heo 103 1.7% Al Viro 95 1.5% Patrick McHardy 93 1.5% Adrian Bunk 92 1.5% FUJITA Tomonori 91 1.5% Avi Kivity 72 1.2% Andrew Morton 71 1.1% Greg Kroah-Hartman 62 1.0% Alan Cox 58 0.9% David Brownell 56 0.9% Jeff Garzik 55 0.9% Christoph Hellwig 54 0.9% Stephen Hemminger 53 0.9% H. Peter Anvin 52 0.8% Jesper Juhl 52 0.8%

By changed lines Adrian Bunk 73254 11.0% Jeff Garzik 43253 6.5% Jens Axboe 28004 4.2% Hirokazu Takata 20399 3.1% Yoichi Yuasa 18368 2.8% James Smart 15626 2.4% Jeremy Fitzhardinge 15398 2.3% David S. Miller 14752 2.2% Matthew Wilcox 14750 2.2% Christoph Hellwig 14550 2.2% Rusty Russell 9452 1.4% Imre Deak 8925 1.3% Dan Williams 8510 1.3% Ralf Baechle 8345 1.3% Doug Thompson 7310 1.1% Yoshihiro Shimoda 6981 1.1% Marc St-Jean 6888 1.0% Luca Olivetti 6540 1.0% Cyrill Gorcunov 6371 1.0% Latchesar Ionkov 5375 0.8%

Ingo Molnar comes out on top of the changesets column by virtue of getting the CFS scheduler merged - then fixing it. Over half of his patches were accepted after 2.6.23-rc1 came out. Ralf Baechle and Paul Mundt both contributed many changes to architecture-specific trees, Trond Myklebust did a lot of NFS work, and, while David Miller had a number of networking patches, the bulk of his changesets were in the architecture-specific (SPARC) trees. The figures on the "by changed lines" side are dominated by code removals (as described above); Jens Axboe also did a bunch of splice work and merged the "bsg" generic SCSI driver. Hirokazu Takata did a bunch of m32r architecture work. James Smart contributed a number of Fibre Channel changes and Jeremy Fitzhardinge merged the core Xen code.

Once again, we have put some effort into associating patches with the companies that supported this work, with the results shown below. These results should always be taken as approximations; we believe that they are essentially correct, but patches do not come with Paid-for-by: headers, so a certain amount of guessing is always required.

Most active 2.6.23 employers

By changesets (Unknown) 1180 19.0% Red Hat 744 12.0% (None) 559 9.0% IBM 507 8.2% Novell 421 6.8% Intel 184 3.0% Oracle 146 2.4% Renesas Technology 134 2.2% MIPS Technologies 119 1.9% NetApp 116 1.9% (Consultant) 103 1.7% Google 99 1.6% NTT 98 1.6% Sony 93 1.5% Astaro 93 1.5% Linux Foundation 82 1.3% MontaVista 81 1.3% SGI 77 1.2% Qumranet 72 1.2% QLogic 62 1.0%

By lines changed (Unknown) 111777 16.9% (None) 99649 15.0% Red Hat 84224 12.7% IBM 39449 5.9% Oracle 36205 5.5% Renesas Technology 33152 5.0% HP 18718 2.8% Tripeaks 18567 2.8% Novell 17990 2.7% Emulex 15942 2.4% XenSource 15426 2.3% Intel 14962 2.3% Sony 11945 1.8% Analog Devices 10345 1.6% rPath 9678 1.5% MIPS Technologies 9171 1.4% Solid Boot Ltd. 8937 1.3% MontaVista 8065 1.2% PMC-Sierra 6888 1.0% Astaro 6687 1.0%

Red Hat retains its place at the top of the by-changesets list, though its percentage of changes has dropped a bit. By lines changed, developers known to be working on their own time (the "None" entry) beat out all corporate contributors. It is worth noting that much of lines-changed count for those developers is, in fact, lines removed.

Looking at who added Signed-off-by: lines to patches is interesting, especially if one looks at signoffs added by people other than the author of the patch. In this way, one gets an idea of who the gatekeepers are. There is a slight change to how this calculation was done this time around: if a patch carried signoffs from both Linus Torvalds and Andrew Morton, Linus's was not counted. As a result of how the process works, everything that goes through Andrew gets a signoff from Linus; not counting those signoffs gives a more accurate picture of how the review was actually done.

Developers with the most signoffs (total 5653)
Andrew Morton	1247	21.6%
Linus Torvalds	397	6.9%
David S. Miller	381	6.6%
Greg Kroah-Hartman	329	5.7%
Jeff Garzik	287	5.0%
James Bottomley	264	4.6%
Paul Mackerras	223	3.9%
Mauro Carvalho Chehab	150	2.6%
Len Brown	128	2.2%
Ralf Baechle	122	2.1%
Roland Dreier	116	2.0%
Andi Kleen	113	2.0%
Russell King	101	1.8%
Jaroslav Kysela	100	1.7%
John W. Linville	70	1.2%
Tony Luck	65	1.1%
Takashi Iwai	63	1.1%
Jens Axboe	58	1.0%
Martin Schwidefsky	55	1.0%
Ingo Molnar	51	0.9%

One question which comes up sometimes is: how do these numbers look for specific parts of the kernel tree? Your editor duly hacked on his scripts to generate this sort of information. Here is a summary of the results - using the employer by-changesets numbers:

Employer changeset contributions by subsystem
/arch (1428 total) (Unknown) 222 15.5% IBM 198 13.9% Red Hat 128 9.0% (None) 108 7.6% Renesas Technology 101 7.1% MIPS Technologies 89 6.2% Sony 55 3.9% Novell 46 3.2% Intel 46 3.2% rPath 42 2.9%	/block (103 total) NTT 27 26.2% Oracle 15 14.6% (Unknown) 10 9.7% IBM 8 7.8% Red Hat 6 5.8% (None) 5 4.9% Miracle Linux 4 3.9% Computer Consultants 3 2.9% Novell 3 2.9% Sony 3 2.9%
/Documentation (241 total) (Unknown) 66 27.4% Novell 27 11.2% IBM 19 7.9% Oracle 19 7.9% (None) 18 7.5% Intel 16 6.6% Red Hat 13 5.4% (Consultant) 6 2.5% Freescale 5 2.1% NEC 4 1.7%	/drivers (2762 total) (Unknown) 572 20.7% (None) 356 12.9% Novell 237 8.6% Red Hat 236 8.5% IBM 191 6.9% Intel 130 4.7% (Consultant) 68 2.5% NTT 65 2.4% Qumranet 63 2.3% QLogic 61 2.2%
/fs (622 total) Red Hat 107 17.2% Oracle 80 12.9% NetApp 74 11.9% (Unknown) 72 11.6% Novell 63 10.1% IBM 56 9.0% Univ. of Michigan CITI 35 5.6% SGI 26 4.2% (Academia) 19 3.1% SWsoft 17 2.7%	/kernel (938 total) Red Hat 259 27.6% (Unknown) 129 13.8% IBM 119 12.7% Renesas Technology 52 5.5% (None) 44 4.7% Novell 36 3.8% MIPS Technologies 31 3.3% Fujitsu 30 3.2% Intel 28 3.0% Linutronix 27 2.9%
/mm (261 total) IBM 38 14.6% (Unknown) 38 14.6% Renesas Technology 33 12.6% SGI 29 11.1% Novell 24 9.2% Google 19 7.3% Red Hat 13 5.0% (None) 10 3.8% ARM 7 2.7% igel 6 2.3%	/net (833 total) (Unknown) 178 21.4% Astaro 92 11.0% Red Hat 87 10.4% (None) 71 8.5% IBM 53 6.4% Linux Foundation 48 5.8% NetApp 47 5.6% Broadcom 23 2.8% Intel 18 2.2% HP 17 2.0%

From these numbers, one might conclude that Red Hat developers are strong in the core kernel area, but they don't much like writing documentation. There is a lot of "hobbyist" participation in the driver subtree - not a particularly surprising result, since making a specific device work is a common itch for developers to scratch. Academics like to play with filesystems, as do, unsurprisingly, companies like Oracle and NetApp.

Beyond being approximate, all of the numbers shown above will change a bit before the final 2.6.23 release, which is probably at least three weeks away. The patches which will be merged in the coming weeks should all be fixed, though, so the changes will, with any luck at all, be small. All told, 2.6.23 shows an active kernel development community with contributions from a large number of developers - and quite a few companies which employ them. The kernel remains a vibrant and alive base on which to build our free systems.

(Thanks are due to Greg Kroah-Hartman for his contributions to the scripts used to generate these statistics).