Development statistics for the 6.10 kernel

The 6.10 kernel was released on July 14 after a nine-week development cycle. This time around, 13,312 non-merge changesets were pulled into the mainline repository — the lowest changeset count since 5.17 in early 2022. Longstanding tradition says that it is time for LWN to gather some statistics on where the new code for 6.10 came from and how it got to the mainline; read on for the details.

As a reminder, much of the information that follows (and much that doesn't) can be had at any time from the LWN kernel source database, which is available to LWN subscribers.

A total of 1,918 developers contributed to 6.10; that is lower than recent releases but essentially equal to the 1,921 contributors to 6.5 in August of last year. Of those developers, 242 made their first kernel contribution in 6.10. The most active contributors to this release were:

Most active 6.10 developers

By changesets Krzysztof Kozlowski 357 2.7% Kent Overstreet 270 2.0% Andy Shevchenko 226 1.7% Uwe Kleine-König 176 1.3% Darrick J. Wong 160 1.2% Jani Nikula 133 1.0% Matthew Wilcox 125 0.9% Ville Syrjälä 122 0.9% Eric Dumazet 120 0.9% Ian Rogers 102 0.8% Hans de Goede 101 0.8% Dmitry Baryshkov 101 0.8% Christoph Hellwig 94 0.7% Takashi Iwai 94 0.7% Geert Uytterhoeven 90 0.7% Arnd Bergmann 87 0.7% Damien Le Moal 87 0.7% Wolfram Sang 82 0.6% Namhyung Kim 78 0.6% Pierre-Louis Bossart 77 0.6%

By changed lines Dmitry Baryshkov 64636 10.0% Darrick J. Wong 23781 3.7% Philipp Hortmann 18687 2.9% Bingbu Cao 14333 2.2% Boris Brezillon 14090 2.2% Wedson Almeida Filho 10335 1.6% Kent Overstreet 9144 1.4% David Howells 8347 1.3% Bitterblue Smith 6117 0.9% Hans de Goede 5821 0.9% Namhyung Kim 5792 0.9% Ian Rogers 5592 0.9% Arnd Bergmann 5492 0.8% Benjamin Tissoires 4924 0.8% Michal Wajdeczko 4804 0.7% Tushar Vyavahare 4647 0.7% Shahab Vahedi 4629 0.7% Fiona Klute 4485 0.7% Akhil R 4316 0.7% Jordan Rife 4135 0.6%

Krzysztof Kozlowski was the leading contributor of commits to the 6.10 kernel, producing over five changes for every day of this release cycle; this work was focused on refactoring throughout the driver subsystems and devicetree changes. Kent Overstreet's work was mostly focused on fixes for the bcachefs filesystem, but he also implemented much of the memory-allocation profiling subsystem. Andy Shevchenko contributed cleanups throughout the driver tree, Uwe Kleine-König continued the driver-refactoring work that has led to 1,883 changes since the 6.4 release, and Darrick Wong did a lot of work on the XFS filesystem, mostly focused on the in-progress online-repair functionality.

In the lines-changed column, Dmitry Baryshkov removed a number of header files that can be automatically generated at build time. Philipp Hortmann removed a couple of unloved drivers from the staging tree. Bingbu Cao added a number of Intel media drivers, and Boris Brezillon contributed the Panthor driver for Arm Mali GPUs.

The top testers and reviewers this time around were:

Test and review credits in 6.10
Tested-by Daniel Wheeler 141 11.7% Kees Cook 46 3.8% Pucha Himasekhar Reddy 43 3.6% Hans Holmberg 28 2.3% Dennis Maisenbacher 28 2.3% Jarkko Sakkinen 25 2.1% Mark Pearson 24 2.0% Arnaldo Carvalho de Melo 22 1.8% Philipp Hortmann 22 1.8% Atish Patra 17 1.4% Björn Töpel 16 1.3% Sujai Buvaneswaran 15 1.2% Pierre-Louis Bossart 14 1.2% Ryan Roberts 14 1.2%	Reviewed-by Christoph Hellwig 303 3.4% Simon Horman 237 2.7% Bard Liao 165 1.9% Andy Shevchenko 149 1.7% Krzysztof Kozlowski 123 1.4% Konrad Dybcio 118 1.3% David Sterba 116 1.3% AngeloGioacchino Del Regno 105 1.2% Dmitry Baryshkov 104 1.2% Jani Nikula 93 1.1% Kees Cook 90 1.0% Rob Herring 86 1.0% Hans de Goede 85 1.0% Andrew Lunn 85 1.0%

These lists do not change much from one release to the next; the developers who are able to find the time for this sort of work tend to be in it for the long haul.

A total of 203 companies (that we know of) supported work on the 6.10 kernel; the most active of those were:

Most active 6.10 employers
By changesets Intel 2031 15.3% Google 980 7.4% Red Hat 922 6.9% (Unknown) 891 6.7% Linaro 838 6.3% (None) 690 5.2% AMD 610 4.6% Oracle 443 3.3% Meta 424 3.2% SUSE 327 2.5% IBM 321 2.4% Huawei Technologies 301 2.3% Qualcomm 247 1.9% Renesas Electronics 246 1.8% Pengutronix 221 1.7% (Consultant) 214 1.6% NVIDIA 205 1.5% Arm 160 1.2% NXP Semiconductors 135 1.0% Collabora 131 1.0%	By lines changed Intel 88245 13.6% Linaro 86382 13.3% (Unknown) 71831 11.1% Red Hat 46754 7.2% Google 37411 5.8% Oracle 28846 4.4% AMD 25793 4.0% Collabora 21917 3.4% (None) 19151 2.9% Meta 16586 2.6% Microsoft 14554 2.2% NVIDIA 10990 1.7% IBM 10350 1.6% ST Microelectronics 8179 1.3% Bootlin 7746 1.2% Qualcomm 7636 1.2% Realtek 7509 1.2% SUSE 7268 1.1% Arm 7019 1.1% NXP Semiconductors 6910 1.1%

For the most part, this list looks as it usually does. It is worth noting, though, that Intel contributed more than twice as many changesets to 6.10 as any other company — over 15% of the total.

Tree flatness

One of the suggested topics for the upcoming Maintainers Summit (to be held on September 17) was whether the merge tree is too flat. In other words, are there too many maintainers sending pull requests directly to Linus Torvalds rather than going through intermediate-level maintainers? Using the treeplot utility from gitdm, one can see what this tree looks like. An unreadable version appears to the right; clicking on it (preferably on a system with a large monitor) will shed more light.

One conclusion that can be drawn is that, while the tree does indeed seem flat, with a lot of trees feeding directly into the mainline (note that 63 such trees have been collapsed into one line in the diagram), there is also a fair amount of work going through more than one repository as well. There would appear to be a slow trend toward adding levels to the hierarchy — but it is indeed slow.

Another way to look at this is to create a histogram showing how many levels of repository each commit went through:

Trees transited by each commit
Trees	Commits
0	26	26
1	8,242	8,242
2	4,817	4,817
3	227	227

The 26 commits that passed through zero trees before landing in the mainline were those committed directly by Torvalds. Nearly two-thirds of all commits went through a single tree before going upstream, but a substantial number also went through at least one other tree first. Whether that indicates an overly flat tree is hard to say.

One other thing worth noting: the trees shown in red in the plot are those that did not include a signed tag authenticating their creators. Torvalds has been increasingly insistent that pull requests should point to signed tags over the last few years, with the result that nearly every pull request he does now includes a signature. Most subsystem maintainers clearly do the same, but there still an occasional unsigned pull that finds its way upstream.

In any case, it seems evident from the above that, even if the process could always benefit from improvements, it is working reasonably well. The kernel community continues to absorb changes at a high rate and put out releases on a predictable schedule. As of this writing, there are just over 12,000 changesets poised to flow into the mainline from linux-next, so the 6.11 kernel (which will likely be released on September 15, putting the next merge window in the middle of several important conferences) will be busy as well.

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