Development statistics for 2.6.31

The Linux Foundation recently announced the release of an updated version of its kernel authorship report, co-written by LWN editor Jonathan Corbet. The information there is interesting, but, since it stops with the 2.6.30 kernel, it also is ancient history at this point. 2.6.30 came out two full months ago, after all. LWN readers, certainly, are used to more current information. Since 2.6.31 is getting close to ready, it seems like the right time to look at this development cycle and see where the code came from.

As of this writing (just after the release of 2.6.31-rc7), the 2.6.31 development cycle had seen the incorporation of 10,663 non-merge changesets from 1,146 individual developers. These patches added almost 903,000 lines of code and removed just over 494,000 lines, for a net growth of just over 408,000 lines. According to Rafael Wysocki's August 25 report, this work introduced 108 regressions into the kernel, 26 of which still lack a resolution.

The largest individual contributors in the 2.6.31 development cycle were:

Most active 2.6.31 developers

By changesets Ingo Molnar 276 2.6% Peter Zijlstra 260 2.4% Paul Mundt 204 1.9% Takashi Iwai 150 1.4% Bartlomiej Zolnierkiewicz 149 1.4% Steven Rostedt 139 1.3% Tejun Heo 134 1.3% Johannes Berg 133 1.2% Magnus Damm 119 1.1% Mike Frysinger 115 1.1% roel kluin 105 1.0% Greg Kroah-Hartman 101 0.9% Erik Andrén 100 0.9% Paul Mackerras 85 0.8% Mark Brown 85 0.8% Bill Pemberton 82 0.8% Jaswinder Singh Rajput 79 0.7% Ben Dooks 72 0.7% Joe Perches 72 0.7% Alexander Beregalov 71 0.7%

By changed lines Bartlomiej Zolnierkiewicz 220749 18.3% Jerry Chuang 78441 6.5% Forest Bond 50834 4.2% David Daney 40052 3.3% Jerome Glisse 38604 3.2% Vlad Zolotarov 23260 1.9% Ingo Molnar 22614 1.9% James Smart 19209 1.6% Bill Pemberton 17249 1.4% dmitry pervushin 14532 1.2% Greg Kroah-Hartman 13234 1.1% Wai Yew CHAY 12741 1.1% Michael Chan 11887 1.0% Linus Walleij 11626 1.0% Paul Mundt 10735 0.9% Peter Zijlstra 10202 0.8% Zhu Yi 10197 0.8% Ben Dooks 10150 0.8% Johannes Berg 9532 0.8% Kalle Valo 9263 0.8%

Ingo Molnar always shows up near the top of the changeset statistics. He has, as usual, contributed work all over the core kernel and x86 architecture code, but the bulk of his work this time is in the performance counters code; most of Peter Zijlstra's contributions were also in this area. The merging of this fast-changing subsystem caused those two developers to be responsible for 5% of the patches going into the 2.6.31 release. Paul Mundt wrote a vast number of Super-H architecture patches, and Takashi Iwai contributed large numbers of ALSA patches.

#5 on the changesets list is Bartlomiej Zolnierkiewicz, who also comes out on top in terms of the number of lines changed. He contributed a few IDE patches, despite having handed off responsibility for that subsystem, but most of his work went into the cleaning-up of Ralink wireless drivers in the staging tree. This cleanup resulted in the removal of an amazing 208,000 lines of code. Jerry Chuang added the RealTek RTL8192SU wireless driver (to staging), Forest Bond added the VIA Technologies VT6655 driver (to staging), David Daney did a bunch of MIPS work (including adding the Octeon Ethernet driver to the staging tree), and Jerome Glisse added kernel mode setting support for Radeon graphics chipsets.

As we have seen in the past few development cycles, the staging tree is the source of much of the change in the kernel tree. The nature of that change is, itself, changing, though. The rush of adding out-of-tree drivers to the staging tree has slowed considerably; we're starting to see more work dedicated to fixing up the code which is already there.

The developers contributing to 2.6.31 were supported by a minimum of 194 employers. The most active of those were:

Most active 2.6.31 employers

By changesets (None) 1704 16.0% Red Hat 1587 14.9% Intel 878 8.2% (Unknown) 846 7.9% IBM 667 6.3% Novell 614 5.8% Renesas Technology 345 3.2% Fujitsu 223 2.1% (Consultant) 212 2.0% Analog Devices 212 2.0% Oracle 175 1.6% Nokia 131 1.2% AMD 129 1.2% Atheros Communications 118 1.1% MontaVista 104 1.0% Xelerated AB 100 0.9% (Academia) 92 0.9% NetApp 91 0.9% HP 86 0.8% Wolfson Microelectronics 85 0.8%

By lines changed (None) 311803 25.8% Red Hat 124831 10.3% Realtek 78441 6.5% Intel 62559 5.2% Broadcom 51806 4.3% Logic Supply 51401 4.3% (Unknown) 47165 3.9% Cavium Networks 40086 3.3% IBM 39991 3.3% Novell 31979 2.6% Renesas Technology 31674 2.6% (Consultant) 23659 2.0% Emulex 19209 1.6% University of Virginia 17607 1.5% Nokia 16234 1.3% Embedded Alley Solutions 15229 1.3% Creative Technology 12741 1.1% Oracle 11704 1.0% Analog Devices 10760 0.9% Texas Instruments 10639 0.9%

The top group in either category is developers working on their own time, followed by Red Hat, which merged a few large chunks of code this time around.

A look at non-author signoffs (a hint as to which subsystem maintainers admitted the patches into the mainline) shows a continuation of recent trends:

Top non-author signoffs in 2.6.31
Individuals David S. Miller 964 10.1% Ingo Molnar 948 9.9% Greg Kroah-Hartman 582 6.1% John W. Linville 575 6.0% Andrew Morton 569 6.0% Mauro Carvalho Chehab 535 5.6% Linus Torvalds 254 2.7% James Bottomley 237 2.5% Benny Halevy 191 2.0% Paul Mundt 159 1.7%	Employers Red Hat 3686 38.7% Novell 1061 11.1% Intel 829 8.7% Google 572 6.0% (None) 422 4.4% IBM 383 4.0% Linux Foundation 254 2.7% Oracle 228 2.4% Panasas 193 2.0% (Consultant) 168 1.8%

49.8% of the patches going into the mainline for 2.6.31 passed through the hands of developers working for just two companies: Red Hat and Novell. Linux kernel developers work for a large number of companies, but subsystem maintainers are increasingly concentrated in a very small number of places.

In summary, it is a fairly typical development cycle for the kernel in recent times. The number of changes is high (but not a record), as is the number of developers. The transient effect of the staging tree is beginning to fade; it is becoming just another path for drivers heading into the mainline. As a whole, the process seems to be functioning in a smooth and robust manner.

(As always, your editor would like to thank Greg Kroah-Hartman for his assistance in the preparation of these statistics.)

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