Development statistics for the 6.5 kernel

The 6.5 kernel was released on August 27 after a nine-week development cycle. By that time, some 13,561 non-merge changesets had found their way into the mainline repository, the lowest number seen since the 5.15 release (12,377 changesets) in late 2021. Nonetheless, quite a bit of significant work was done in this cycle; read on for a look at where that work came from.

1,921 Developers contributed to 6.5, a slightly lower number than usual; 271 of those developers made their first kernel contribution for this release. The top contributors to the 6.5 kernel were:

Most active 6.5 developers

By changesets Uwe Kleine-König 272 2.0% Krzysztof Kozlowski 235 1.7% Christoph Hellwig 213 1.6% Ian Rogers 198 1.5% Arnd Bergmann 190 1.4% Hans de Goede 140 1.0% David Howells 120 0.9% Lijo Lazar 115 0.8% Johannes Berg 110 0.8% Dmitry Baryshkov 108 0.8% Konrad Dybcio 99 0.7% Mark Brown 96 0.7% Jani Nikula 96 0.7% Thomas Gleixner 91 0.7% Oswald Buddenhagen 91 0.7% Christophe JAILLET 88 0.6% Nishanth Menon 87 0.6% Andy Shevchenko 85 0.6% Jakub Kicinski 84 0.6% Thomas Zimmermann 74 0.5%

By changed lines Ian Rogers 26662 4.3% Zong-Zhe Yang 20395 3.3% Jakub Kicinski 17505 2.8% Hawking Zhang 16730 2.7% Mark Rutland 14829 2.4% Ping-Ke Shih 11090 1.8% Rohit Agarwal 8669 1.4% Benjamin Gaignard 8275 1.3% Takashi Iwai 7675 1.2% Hans de Goede 6112 1.0% Jonathan Kim 5820 0.9% Le Ma 5337 0.9% Jani Nikula 5334 0.9% Konrad Dybcio 5263 0.8% Bryan O'Donoghue 5119 0.8% Christoph Hellwig 4924 0.8% David Howells 4848 0.8% Pawel Laszczak 4827 0.8% Dmitry Baryshkov 4773 0.8% Johannes Berg 4748 0.8%

As was the case for 6.4, Uwe Kleine-König tops the list of individual contributors as measured by number of changesets, again mostly for work changing the internal platform-device driver API. Krzysztof Kozlowski is, again as with 6.4, in the second spot, having contributed a lot of devicetree changes. Christoph Hellwig continues refactoring code in the block and filesystem layers, with much of his work being in the Btrfs filesystem this time around. Ian Rogers (again, as with 6.4) contributed a lot of changes to the perf tool, and Arnd Bergmann made fixes all over the kernel tree.

Rogers touched the most lines of code this time around (in a cycle that featured relatively few large commits) by updating various vendor-specific perf events. Zong-Zhe Yang contributed 25 changes to the rtw89 WiFi driver, Jakub Kicinski added code to the ynl tool, Hawking Zhang added a relatively restrained set of amdgpu headers, and Mark Rutland reorganized and documented a number of low-level locking primitives.

The top testers and reviewers for this cycle were:

Test and review credits in 6.5
Tested-by Daniel Wheeler 165 11.5% Michael Kelley 63 4.4% Kan Liang 44 3.1% Guilherme G. Piccoli 40 2.8% Helge Deller 38 2.6% Oleksandr Natalenko 37 2.6% Heiko Stuebner 32 2.2% Randy Dunlap 25 1.7% Naama Meir 21 1.5% Rafal Romanowski 19 1.3% Pucha Himasekhar Reddy 19 1.3%	Reviewed-by Simon Horman 276 3.1% Konrad Dybcio 220 2.5% Christoph Hellwig 218 2.5% Hawking Zhang 161 1.8% Kees Cook 153 1.7% Andy Shevchenko 147 1.7% David Sterba 142 1.6% Krzysztof Kozlowski 142 1.6% Felix Kuehling 138 1.6% Conor Dooley 115 1.3% Dmitry Baryshkov 113 1.3%

There are two developers who are credited with having tested at least one patch for every day in this 63-day cycle, and 25 who reviewed at least one patch per day. Simon Horman, who reviews patches in the network subsystem, sustained a rate of over four per day. Overall, 1,177 (8.7%) of the commits in 6.5 had Tested-by tags, and 6,702 (49%) had Reviewed-by tags, continuing the longstanding, gradual increase in the use of those tags.

A total of 218 employers (that we were able to identify) supported work on the 6.5 kernel; the most active of those were:

Most active 6.5 employers

By changesets Intel 1503 11.1% AMD 1233 9.1% Linaro 1174 8.7% Google 922 6.8% (Unknown) 838 6.2% Red Hat 777 5.7% (None) 623 4.6% NVIDIA 381 2.8% SUSE 366 2.7% Huawei Technologies 347 2.6% Pengutronix 326 2.4% Qualcomm 303 2.2% Oracle 293 2.2% Meta 265 2.0% (Consultant) 261 1.9% IBM 236 1.7% Texas Instruments 193 1.4% Arm 180 1.3% Renesas Electronics 151 1.1% Collabora 147 1.1%

By lines changed Intel 66098 10.7% AMD 65508 10.6% Google 46208 7.4% Linaro 41969 6.8% Realtek 34719 5.6% (Unknown) 31602 5.1% Red Hat 26304 4.2% Qualcomm 23527 3.8% Meta 22721 3.7% Arm 18813 3.0% Collabora 16801 2.7% (None) 16168 2.6% SUSE 15021 2.4% NVIDIA 12800 2.1% Texas Instruments 11308 1.8% Oracle 8627 1.4% Huawei Technologies 7908 1.3% IBM 7311 1.2% (Consultant) 6897 1.1% MediaTek 6562 1.1%

The list of companies working on the kernel tends not to change much — at the upper end of the list, anyway. This list says little about what these companies are up to in the kernel, though. Below is a summary, for some of the top corporations, of the number of changesets touching some of the more active areas of the kernel (and the percentage that makes of the company's total contribution):

	AMD		Google	Intel	Linaro	NVIDIA	Red Hat	(None)	(Unknown)
Architecture	65	5%	213	23%	114	8%	347	30%	15	4%	40	5%	111	18%	135	17%
Core kernel	33	3%	182	20%	147	10%	74	6%	15	4%	51	7%	75	12%	53	7%
Block/filesystem	0	0%	62	7%	19	1%	15	1%	0	0%	154	21%	26	4%	42	5%
Drivers	1,106	91%	199	22%	1064	73%	597	52%	275	75%	286	39%	366	60%	413	51%
Networking	10	1%	74	8%	313	21%	60	5%	221	60%	133	18%	79	13%	104	13%
Tools	17	1%	235	26%	55	4%	17	1%	58	16%	112	15%	5	1%	41	5%
Documentation	27	2%	39	4%	29	2%	148	13%	15	4%	31	4%	53	9%	97	12%

This table gives some idea of where the top contributors put their effort in the kernel. The sharp-eyed may notice that the percentages do not add up to 100%; that is primarily because many changes touch more than one subsystem, and are thus counted more than once.

It will not be surprising to see that the hardware-manufacturing companies — AMD, Intel, and NVIDIA — focus their work in the driver subsystem. They are here first and foremost to ensure that their products work well with Linux, and that means working on drivers. Perhaps a bit more surprising is that these companies, all of which make CPUs, do not make many changes to the architecture-support code (or, at least, did not do that during the 6.5 development cycle). Google's commit count under arch/ exceeded that of those other three companies combined.

Linaro, which exists to support the Arm architecture, does put a fair amount of effort into the arch/ subtree. Lest one think that Linaro is a documentation champion, though, one should remember that the devicetree bindings live under Documentation/. That work is really more hardware support in the end. Of the groups listed above, developers with no known affiliation (the "None" and "Unknown" columns) are seemingly the most enthusiastic, percentage-wise, about contributing to the documentation.

A lot of work, from some companies at least, is done in the tools/ subtree. Activity there is focused on the perf tool, the growing self-test suite, the objtool utility that is an ever-more important part of the build process, and more. An increasing amount of the code in the kernel tree runs in user space.

Kernel development goes through periods of high and low activity; 6.5 was a slow cycle (though, clearly, in relative terms), but 6.6 might pick up the pace a bit. There are 11,642 non-merge changesets queued there as of this writing. At times, it seems, there is simply less work needing to be done. Experience says, though, that the patch rate will pick up again before too long; the kernel project, it seems, is never done.

Index entries for this article
Kernel	Releases/6.5

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