Who wrote 2.6.32

In particular, as of this writing (shortly after the 2.6.32-rc8 release), 2.6.32 is the result of 10,767 non-merge changesets sent in by 1,229 developers. This changes added a total of 1.17 million lines, while removing 611,000 lines, for a net growth of 559,000 lines of code. According to Rafael Wysocki's regression reports, this development cycle introduced a total of 86 regressions into the kernel - slightly fewer than we saw for 2.6.31. As of that posting, the number of unresolved regressions was shrinking quickly, with 25 of them still without a resolution.

So who added all those regressions lines of code? The statistics for this cycle look like this:

Most active 2.6.32 developers

By changesets Greg Kroah-Hartman 202 1.9% Johannes Berg 180 1.7% Bartlomiej Zolnierkiewicz 164 1.5% Mark Brown 154 1.4% Paul Mundt 139 1.3% Takashi Iwai 139 1.3% Alan Cox 129 1.2% Roel Kluin 115 1.1% Luis R. Rodriguez 105 1.0% Dan Williams 86 0.8% Tejun Heo 84 0.8% Herbert Xu 81 0.8% Peter Zijlstra 80 0.7% Ingo Molnar 77 0.7% Julia Lawall 77 0.7% Steven Rostedt 73 0.7% Magnus Damm 72 0.7% Joe Perches 71 0.7% Joerg Roedel 70 0.7%

By changed lines Greg Kroah-Hartman 174427 11.5% Bartlomiej Zolnierkiewicz 108056 7.1% Mauro Carvalho Chehab 62719 5.2% Jing Huang 49189 3.2% Forest Bond 45009 3.0% Ben Hutchings 37418 2.5% Eilon Greenstein 28008 1.8% Mark Brown 24516 1.6% Brian Swetland 22775 1.5% Hank Janssen 19681 1.3% Leo Chen 17458 1.2% Palash Bandyopadhyay 16790 1.1% Alan Cox 16466 1.1% Mithlesh Thukral 15173 1.0% Jerome Glisse 14343 0.9% Michael Chan 13415 0.9% Martyn Welch 12480 0.8% Iliyan Malchev 12172 0.8% Jesse Brandeburg 11051 0.7%

As has become traditional, Greg Kroah-Hartman and Bartlomiej Zolnierkiewicz feature at the top of both lists. Much of Greg's work had to do with the cleaning up of Microsoft's "hv" drivers. His state of mind during this process is best assessed from the commit messages, which tend to read like this one:

Greg also removed some drivers from the staging tree, shrinking the kernel by over 100,000 lines.

The bulk of Bartlomiej's work is also in the staging tree, and that is mostly concerned with fixing up a series of rather unloved wireless network drivers. These patches are somewhat controversial; the wireless developers would rather see that effort going into a different set of non-staging drivers. But those drivers are not yet ready for prime time, and, meanwhile, people are using the staging drivers. Wireless drivers were also the focus of Johannes Berg's work; he has made a long set of improvements to the mac80211 subsystem and its cfg80211 configuration interface. Mark Brown continues to contribute large amounts of code in support of Wolfson Micro's components, and Paul Mundt remains active as the Super-H maintainer.

In the "lines changed" column, Mauro Carvalho Chehab contributed a lot of patches as the Video4Linux2 maintainer. Jing Huang contributed the Brocade BFA FC SCSI driver, and Forest Bond added the VT6656 wireless driver to the staging tree.

Developers working on 2.6.32 were supported by (at least) 196 employers. The most active companies this time around are:

Most active 2.6.32 employers

By changesets (None) 1845 17.1% Red Hat 1028 9.5% (Unknown) 933 8.7% Intel 888 8.2% Novell 662 6.1% IBM 603 5.6% Oracle 319 3.0% Renesas Technology 264 2.5% AMD 251 2.3% Nokia 204 1.9% Fujitsu 201 1.9% Atheros Communications 197 1.8% (Consultant) 195 1.8% (Academia) 167 1.6% Texas Instruments 155 1.4% Wolfson Micro 153 1.4% Broadcom 149 1.4% HP 130 1.2% Analog Devices 124 1.2% Pengutronix 119 1.1%

By lines changed (None) 282017 18.6% Novell 256808 16.9% Red Hat 150781 9.9% Broadcom 84904 5.6% Intel 79267 5.2% (Unknown) 77122 5.1% Brocade 49189 3.2% Logic Supply 45165 3.0% Google 40936 2.7% IBM 29616 2.0% Wolfson Micro 25577 1.7% Texas Instruments 24824 1.6% Renesas Technology 24507 1.6% Nokia 24192 1.6% Microsoft 19696 1.3% Oracle 19410 1.3% (Consultant) 18774 1.2% Conexant 16790 1.1% LinSysSoft Technologies 15173 1.0% GE Fanuc 12495 0.8%

The sharp-eyed reader will notice that Red Hat has fallen below 10% of the total changes - the first time that has happened since the 2.6.21 development cycle in early 2007. The number of changes from Red Hat this time around is only slightly lower than the usual, though; what's happening is that some of the other companies are catching up.

There are a couple of other interesting entries here. Google takes a lot of grief for not contributing back, but that company was the source of a fair amount of code going into 2.6.32. Much of that was support for the HTC "Dream" (aka G1 or ADP1) phone platform, but Google also contributed to control groups, ext4, memory management, IPVS, and libata. And one may have never expected to see Microsoft show up on the list of top kernel contributors, but the hv drivers put it there for 2.6.32.

The numbers for signoffs have not changed much from previous cycles:

Top non-author signoffs in 2.6.32
Individuals David S. Miller 996 10.2% John W. Linville 994 10.2% Greg Kroah-Hartman 788 8.1% Andrew Morton 786 8.1% Ingo Molnar 501 5.1% Mauro Carvalho Chehab 398 4.1% James Bottomley 310 3.2% Len Brown 188 1.9% Paul Mundt 171 1.8% Russell King 165 1.7%	Employers Red Hat 3606 37.1% Novell 1309 13.5% Intel 906 9.3% Google 793 8.2% (None) 445 4.6% IBM 384 3.9% (Consultant) 274 2.8% Renesas Technology 180 1.9% Wolfson Micro 155 1.6% Oracle 138 1.4%

If anything, the subsystem maintainers are concentrating even more than before. Fully 2/3 of the patches going into the mainline kernel pass through the hands of developers working for just four companies.

At the 2009 Kernel Summit, the participants concluded that, while improvements can always be made, the process as a whole is working well. The picture that comes from these numbers suggests the same conclusion: the kernel development machine continues to absorb massive numbers of changes from a wide development community while continuing to produce stable, increasingly functional releases.