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Some 4.5 Development statistics

By Jonathan Corbet
March 9, 2016
When Linus released the 4.5-rc7 prepatch, he indicated that it would probably be the last one prior to the official 4.5 release. That means we're running a bit late for the traditional article full of statistics for this development cycle. So, without further ado, here is a look at the changes that came in during the 4.5 cycle and where they came from.

As of this writing, just over 12,000 non-merge changesets have landed in the mainline repository for 4.5. That makes 4.5 one of the quieter development cycles in the last year; less than 4.2 and 4.4 (both over 13,000 changesets) but approximately equal to 4.1 and 4.3. All things are relative, of course; not that long ago, 12,000 changes would have been one of the busiest cycles. Even when the kernel community slows down a bit, there is a lot going on.

These changes were contributed by 1,528 developers — short of the 1,575 seen in 4.4 or the 1,625 in 4.3, but, once again, a fair crowd of contributors. The most active of these developers were:

Most active 4.5 developers
By changesets
Linus Walleij2362.0%
Arnd Bergmann2261.9%
Leo Kim2101.7%
Mauro Carvalho Chehab1691.4%
Geert Uytterhoeven1591.3%
Ville Syrjälä1261.0%
Kuninori Morimoto1120.9%
Takashi Iwai1080.9%
Jiri Olsa1040.9%
Christoph Hellwig1020.8%
Julia Lawall1010.8%
Glen Lee1010.8%
Javier Martinez Canillas890.7%
Geliang Tang890.7%
Dan Carpenter850.7%
Daniel Vetter810.7%
Boris Brezillon800.7%
Alex Deucher800.7%
Kirill A. Shutemov770.6%
Thierry Reding740.6%
By changed lines
Doug Ledford530867.7%
Tomi Valkeinen366315.3%
Eric Huang227143.3%
Alex Deucher166042.4%
yanyang1111291.6%
Igal Liberman105691.5%
Thierry Reding98421.4%
Bard Liao97621.4%
Christoph Hellwig96801.4%
Arnd Bergmann92331.3%
Geert Uytterhoeven83251.2%
Stephen Boyd81831.2%
Paul E. McKenney74851.1%
Rex Zhu73821.1%
The etnaviv authors72381.1%
Jammy Zhou71751.0%
Mauro Carvalho Chehab64730.9%
Eric Anholt62340.9%
Maruthi Srinivas Bayyavarapu52390.8%
Adam Thomson51530.7%

Linus Walleij topped the by-changesets list with a lot of low-level work, mostly near the GPIO subsystem and drivers that use it. Arnd Bergmann works all over the tree, mostly dealing with build problems and improving ARM multiplatform support. Leo Kim worked exclusively on cleaning up the wilc1000 driver in the staging tree, Mauro Carvalho Chehab made many improvements as the maintainer of the media subsystem, and Geert Uytterhoeven did a lot of work in the ARM and related driver subsystems.

In many development cycles, this list has been dominated by developers working in the staging subsystem, but 4.5 is an exception: only two of the developers in the by-changesets column had any significant work in the staging tree at all. Both of them, as it turns out, were working on the wilc1000 driver.

In the lines-changed column, longtime contributor Doug Ledford got to the top with three changesets removing three unloved staging drivers, deleting 53,000 lines of code. Tomi Valkeinen did a lot of work with the TI OMAP subarchitecture, while Eric Huang, Alex Deucher, and "yanyang1" all added functionality to the AMD graphics drivers. Further down that list, "the etnaviv authors" is an alias that was used for a single patch adding the Etnaviv graphics driver; it represents the work of Christian Gmeiner, Russell King, and Lucas Stach.

Work on the 4.5 kernel was supported by just over 200 companies that we could identify — a typical number. The employers supporting the most work this time were:

Most active 4.5 employers
By changesets
Intel173414.4%
(Unknown)9758.1%
Red Hat7326.1%
Linaro7236.0%
(None)6285.2%
Samsung5134.3%
SUSE3823.2%
Atmel3803.2%
Renesas Electronics3603.0%
IBM3462.9%
AMD2832.4%
Mellanox2752.3%
(Consultant)2452.0%
Broadcom2081.7%
Oracle1791.5%
Google1601.3%
Texas Instruments1521.3%
Huawei Technologies1411.2%
NVidia1371.1%
ARM1271.1%
By lines changed
Red Hat8365712.1%
Intel8016011.6%
AMD7467310.8%
Texas Instruments418086.1%
(Unknown)279584.1%
IBM254333.7%
Linaro221983.2%
(None)219293.2%
Mellanox195582.8%
Samsung191902.8%
Renesas Electronics179642.6%
(Consultant)155932.3%
NVidia150382.2%
Freescale139642.0%
Code Aurora Forum135142.0%
Atmel108451.6%
Realtek100901.5%
Rockchip97351.4%
Huawei Technologies79921.2%
Broadcom79301.2%

Intel is, by now, the dominant contributor; it would have been at the top of both lists except for the aforementioned drivers removed by Doug Ledford. Red Hat, which once reliably sat at the top of the list, may soon be overshadowed by companies working in the mobile and embedded space. In general, though, this table looks much like it has for some time.

If we look at non-author signoffs — the addition of Signed-off-by tags to patches by developers other than the author — the story looks just a little different:

Most non-author signoffs in 4.5
Developers
Greg Kroah-Hartman10099.0%
David S. Miller9508.5%
Mark Brown5855.2%
Andrew Morton4514.0%
Martin K. Petersen2642.4%
Arnaldo Carvalho de Melo2632.3%
Mauro Carvalho Chehab2352.1%
Glen Lee2101.9%
Rafael J. Wysocki2051.8%
Kalle Valo1931.7%
Companies
Red Hat198117.8%
Intel145913.1%
Linux Foundation10299.2%
Linaro10039.0%
Google6325.7%
Samsung4474.0%
(None)3613.2%
Oracle2952.7%
IBM2882.6%
SUSE2652.4%

To a first approximation, this table represents the most active subsystem maintainers — the developers who make the decision to accept any given patch. While the more traditional, enterprise-oriented companies remain at the top of this list, the curve has been flattening over time as more companies take responsibility for the maintenance of parts of the kernel.

Finally, it has been a while since we looked at what the most active companies are most interested in. That is a simple matter of picking out the patches contributed by a given company's developers and noting which files were touched. So, for example, here is where Intel works:

Intel
%Subsystem Notes
67%drivers/ 29% gpu, 15% net, 5% staging
12%include/
9%sound/
5%net/
5%arch/ 3.3% x86
4%kernel/
4%mm/

Intel, clearly, is focused on drivers for its hardware and CPUs, as one might expect. The picture for Red Hat is a bit different:

Red Hat
%Subsystem Notes
29%drivers/ 6% gpu, 5% net, 3% tty
22%tools/19% perf
17%fs/ 4% xfs, 3% nfs, 3% gfs2, 2% namei.c, 1% btrfs, 1% ceph, 1% f2fs, 1% ext4
14%include/
13%arch/ 4% x86, 2% arm, 2% s390, 1% powerpc, 1% sparc
7%kernel/
5%net/
3%crypto/

Red Hat's contribution to the tools directory (and the perf tool in particular) has increased over the years, but the company still works all over the kernel, putting a significant part of its effort into the core kernel code.

What about Linaro, which has been increasing its contributions over the years?

Linaro
%Subsystem Notes
66%drivers/ 17% gpio, 7% clocksource, 7% pinctrl, 4% mfd, 4% staging, 4% net
25%arch/ 19% arm, 4% arm64, 1% mips
6%include/
3%sound/
3%Documentation/

Linaro is all about hardware enablement, and its work shows that. Even the work in the documentation directory is aimed that way: almost all of it happened in the devicetree subdirectory. (Lest anybody worry that the numbers add up to over 100%, remember that many patches touch more than one subdirectory, and are thus counted more than once).

Many of the other companies on the list have similar patterns; they tend to be interested in support for their own hardware, so that is where their work is done. Something slightly different can be seen if one skips down the list and looks at Google, though:

Google
%Subsystem Notes
29%drivers/ 9% net, 8% input, 5% usb, 4% md, 3% pci
31%net/ 15% ipv4, 9% core, 8% ipv6
17%include/
15%arch/ 10% x86, 3% powerpc, 2% arm, 2% arm64
6%fs/ 3% ext4

Many of the improvements to the networking subsystem have, in recent years, come from Google; the numbers here show that Google is still interested in making Linux networking better.

All of this activity is the result of around 200 companies and numerous individuals, all working in pursuit of their own interests without any sort of overall control. As one might expect, the outcome can be a bit patchy at times; less energy goes into areas like documentation and security than one might like. But we still get a quickly evolving, highly capable kernel out of it, and that doesn't look like it will change anytime soon.

Index entries for this article
KernelReleases/4.5


to post comments

Some 4.5 Development statistics

Posted Mar 10, 2016 8:43 UTC (Thu) by pbonzini (subscriber, #60935) [Link] (2 responses)

How do the numbers add up for non-author signoffs? Greg K-H and Andrew Morton are both employed by the Linux Foundation, and they have 1460 signoffs in total.

Some 4.5 Development statistics

Posted Mar 10, 2016 11:13 UTC (Thu) by corbet (editor, #1) [Link] (1 responses)

Andrew left the Linux Foundation. He's only been at Google since 2006, so I can understand why maybe not everybody has caught up :)

Some 4.5 Development statistics

Posted Mar 10, 2016 14:30 UTC (Thu) by pbonzini (subscriber, #60935) [Link]

Oops. :) He still uses the linxfoundation.org email though.

Let's put it like this, the effort you put in generating these stats for every release is commendable.


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