Development statistics for 6.4

The 6.4 kernel was released on June 25 after a nine-week development cycle. By that point, 14,835 non-merge changesets had been pulled into the mainline kernel, a slight increase from 6.3 (14,424 changesets) but still lower than many other development cycles. As usual, LWN has taken a look at those changesets, who contributed them, and what the most active developers were up to.

The work in 6.4 was contributed by 1,980 developers, 282 of whom made their first kernel contribution during this development cycle. The most active 6.4 developers were:

Most active 6.4 developers

By changesets Uwe Kleine-König 781 5.3% Krzysztof Kozlowski 499 3.4% Rob Herring 200 1.3% Ian Rogers 200 1.3% Konrad Dybcio 146 1.0% Thomas Zimmermann 132 0.9% AngeloGioacchino Del Regno 126 0.8% Hans de Goede 121 0.8% Christoph Hellwig 118 0.8% Ville Syrjälä 116 0.8% Tom Rix 115 0.8% Nick Alcock 112 0.8% Johannes Berg 111 0.7% Darrick J. Wong 111 0.7% Philipp Hortmann 101 0.7% Geert Uytterhoeven 88 0.6% Greg Kroah-Hartman 87 0.6% Manivannan Sadhasivam 85 0.6% Eric Dumazet 84 0.6% Bart Van Assche 83 0.6%

By changed lines Ian Rogers 167443 17.4% Hawking Zhang 123915 12.8% Eduard Zingerman 25322 2.6% Laurent Pinchart 17210 1.8% Ping-Ke Shih 16062 1.7% Darrick J. Wong 11027 1.1% Uwe Kleine-König 10159 1.1% Benjamin Tissoires 8623 0.9% Konrad Dybcio 8421 0.9% Jani Nikula 7982 0.8% Jiri Slaby 7645 0.8% AngeloGioacchino Del Regno 7353 0.8% Krzysztof Kozlowski 7285 0.8% Hans de Goede 7068 0.7% Paul Gortmaker 7011 0.7% Tony Nguyen 6834 0.7% Jeffrey Hugo 6718 0.7% Wolfram Sang 6665 0.7% Devi Priya 6036 0.6% Qu Wenruo 5617 0.6%

The 6.3 merge window included a patch from Uwe Kleine-König adding a new function pointer to struct platform_driver. Noting that the driver core ignores the return value from the remove() function, he decided to make that function return void instead. There are, however, many drivers defining that function — more than could be changed at that time. So, rather than changing remove(), he added remove_new(), which behaves in the same way with the exception that it returns void; that made it possible to convert drivers at leisure.

"At leisure" may not describe what happened in 6.4, though, where Kleine-König contributed 781 changesets, almost all of them converting drivers to remove_new(). It's worth noting that we are likely to see a repeat of this performance; the plan calls for renaming remove_new() back to remove() (and updating all the drivers again) once the conversion is complete. Krzysztof Kozlowski, whose work (mostly in the devicetree subtree) would have normally put him easily into the top position, came in a distant second this time around. Ian Rogers made a number of enhancements to the perf tool, Rob Herring worked mostly on devicetree improvements, and Konrad Dybcio hacked on various system-on-chip drivers and devicetree files.

Rogers also made it to the top of the "lines changed" column by contributing updated event definitions for perf. Hawking Zhang added the obligatory set of amdgpu register definitions. Eduard Zingerman reworked many of the BPF self-tests, adding a lot of inline assembly code; this patch is a typical example. Laurent Pinchart deleted a number of unused camera-sensor drivers while adding the i.MX8 ISI driver, and Ping-Ke Shih added a set of static tables to the rtw89 WiFi driver.

The top testers and reviewers this time around were:

Test and review credits in 6.4
Tested-by Daniel Wheeler 159 12.9% Chen-Yu Tsai 61 5.0% Marek Szyprowski 36 2.9% Abhinav Kumar 27 2.2% Sachin Sant 21 1.7% Joel Fernandes 20 1.6% Zqiang 18 1.5% Tommaso Merciai 17 1.4% Philipp Hortmann 16 1.3% Tony Zhu 16 1.3% Arnaldo Carvalho de Melo 15 1.2% Marek Szlosek 15 1.2%	Reviewed-by Simon Horman 327 3.9% Konrad Dybcio 208 2.5% Krzysztof Kozlowski 197 2.4% AngeloGioacchino Del Regno 151 1.8% David Sterba 134 1.6% Rob Herring 127 1.5% Chen-Yu Tsai 118 1.4% Dmitry Baryshkov 116 1.4% Dave Chinner 115 1.4% Hans de Goede 113 1.4% Christoph Hellwig 112 1.3% Geert Uytterhoeven 104 1.3%

For 6.4, 1,064 commits (7% of the total) carried Tested-by tags, while 6,392 (43%) had Reviewed-by tags. That is a significant drop since 6.3 for both types of tags. The Tested-by tags, in particular, clearly do not reflect the actual testing activity that is taking place in the kernel community.

A total of 230 employers (that could be identified) supported work on 6.4, a slight increase from 6.3. The most active employers were:

Most active 6.4 employers

By changesets Intel 1542 10.4% Linaro 1505 10.1% Google 1137 7.7% (Unknown) 1086 7.3% Red Hat 881 5.9% Pengutronix 826 5.6% AMD 624 4.2% (None) 582 3.9% Meta 467 3.1% Oracle 384 2.6% NVIDIA 381 2.6% SUSE 355 2.4% IBM 349 2.4% Qualcomm 300 2.0% (Consultant) 262 1.8% Collabora 236 1.6% Renesas Electronics 224 1.5% Huawei Technologies 221 1.5% NXP Semiconductors 195 1.3% Microsoft 183 1.2%

By lines changed Google 191963 19.9% AMD 156235 16.2% Intel 73179 7.6% (Unknown) 67648 7.0% Linaro 42260 4.4% Red Hat 39293 4.1% Qualcomm 28096 2.9% (None) 23696 2.5% (Consultant) 23488 2.4% SUSE 23393 2.4% Meta 20978 2.2% Realtek 20830 2.2% NVIDIA 19050 2.0% Oracle 16942 1.8% IBM 15768 1.6% Renesas Electronics 14519 1.5% Pengutronix 11598 1.2% MediaTek 10956 1.1% Collabora 10066 1.0% Microsoft 9824 1.0%

As usual, there are not a lot of surprises to be found in these results.

"Lines changed" is, like commit counts, a poor proxy for software productivity, but it's hard to find a better one. So, your editor has concluded, one might as well just go nuts with the "lines changed" metric over the long term. With the use of git blame and a certain amount of CPU time, it is possible to look at who is "blamed" for every line in the kernel source — who is the last developer to have touched it, in other words.

Running this analysis on the 6.4-rc7 kernel turns up 22,612 developers who have touched at least one line — 2,135 of whom have touched exactly one line. The developers who have left the biggest imprint on the 6.4 kernel are:

Developer	Lines	Pct
Linus Torvalds	2159025	5.9%
Alex Deucher	1177105	3.2%
Hawking Zhang	840838	2.3%
Huang Rui	479002	1.3%
Mauro Carvalho Chehab	417086	1.1%
Aurabindo Pillai	383629	1.1%
Oded Gabbay	292611	0.8%
Ian Rogers	271905	0.7%
Leo Li	228680	0.6%
Bhawanpreet Lakha	206275	0.6%
Qingqing Zhuo	198516	0.5%
Aaron Liu	193174	0.5%
Ping-Ke Shih	184453	0.5%
Larry Finger	172346	0.5%
Ben Skeggs	170190	0.5%
Roman Li	164743	0.5%
Mark Brown	158765	0.4%
David Howells	158530	0.4%
Hans de Goede	157719	0.4%
Laurent Pinchart	145900	0.4%
James Smart	145427	0.4%
Kalle Valo	144362	0.4%
Hans Verkuil	142093	0.4%
Johannes Berg	139245	0.4%
Takashi Iwai	131543	0.4%
Feifei Xu	127510	0.4%
Christoph Hellwig	127129	0.3%
Thierry Reding	118462	0.3%
Linus Walleij	115289	0.3%
David S. Miller	97207	0.3%

Torvalds does not write a lot of kernel code these days, and hasn't for some time; his position at the top of the list is the enduring legacy of the initial Git commit of the 2.6.12 kernel in 2005. Many of the other developers on that list — Alex Deucher, Hawking Zhang, Huang Rui, Aurabindo Pillai, Leo Li, Qingqing ZHuo, Aaron Liu, and Roman Li — are there primarily as the result of having contributed amdgpu header files, though Deucher's work is quite a bit broader than that. Mauro Carvalho Chehab has left such a big footprint after many years of intensive work in the media subsystem and the conversion of much kernel documentation to the RST format.

A few of the developers on the above list are there as the result of consistent kernel work over a period of decades, but that clearly is not the main variable being measured here. Those wanting to see more can view the top 2,000 results separately. Note that no attempt has been made to join multiple entries resulting from name changes, typos, or mailing-list mangling.

As of this writing, there are about 11,330 changesets waiting in linux-next for the 6.5 merge window. LWN will, of course, be watching as that work pours into the mainline and yet another development cycle runs its course. The kernel development community continues to run at full speed.

Index entries for this article
Kernel	Releases/6.4

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