Linux creator Linus Torvalds has released an experimental kernel branch developed with Anthropic’s Claude Code coding assistant, addressing page cache contention and tripling small-read throughput on his test machine, while defending the role of AI in lowering barriers for programmers.
A new branch titled noref-filemap-read-with-llm appeared in the Linux repository, marking a change in how the project’s founder engages with generative artificial intelligence. The code targets a specific memory management bottleneck where multiple threads make small reads from the same file and contend over reference counting in the page cache.
Claude Code Rewrites Linux Memory Management
Michael Larabel reported in Phoronix that he had spotted the experimental branch in the personal Linux repository of Linus Torvalds. Torvalds confirmed in the patch cover letter that the implementation, tests, review, and initial documentation were generated by an LLM coding assistant under his direct supervision. The experiment consists of eight patches targeting how Linux reads data from its page cache, focusing specifically on how the operating system keeps track of memory pages. The branch sits on top of Linux 7.3-rc6 and was tested on Torvalds’ own laptop. The suffix in the branch name leaves no ambiguity about its origins, with Torvalds confirming that the code, test programs, review behind the patch list, and the first draft of the cover letter were produced by Claude Code working under his direction. The measurements were run on his own machine using a four-core, eight-thread laptop with an Intel Core i7-8565U processor and mitigations disabled.
“The code, the test programs, the review behind the list above and the first draft of this text were done with an LLM coding assistant (Claude Code) under my direction. The measurements were run on my machine.”
Linus Torvalds, Linux kernel creator
Benchmarks run on Torvalds’ four-core, eight-thread laptop with an Intel Core i7-8565U processor showed dramatic gains for concurrent small reads. With eight threads reading the same file, throughput jumped from roughly 9.9 to 10.4 million reads per second up to between 30 and 33 million, while the cost per read dropped from about 2,950 cycles to approximately 725. Operating across four separate CPU cores, a four-thread workload saw its performance grow from around 9–12 million reads per second up to the 25–26 million range.
| Workload Configuration | Base Performance | Series Performance |
|---|---|---|
| Read cost, 8 threads same file (~2,950 cycles vs ~725 cycles) | ~2,950 cycles | ~725 cycles |
| Throughput, 8 threads same file (9.9–10.4 M reads/s vs 30–33 M reads/s) | 9.9–10.4 M reads/s | 30–33 M reads/s |
The optimization carries trade-offs. A single-threaded test touching an unmapped page grew slower, rising from about 4,150 to 6,550 cycles due to new bookkeeping overhead when concurrency cannot amortize the cost, while a single-threaded test showed a smaller improvement by rising from about eight million to nearly nine million reads per second.
Torvalds Discusses AI Content and Maintainer Burnout at Open Source Summit Europe
Torvalds spoke with Dirk Hohndel, head of Ericsson Software Technology, during their discussion at the event organized by the Linux Foundation in Prague, Czech Republic, where IT outlet TechRadar reported on his remarks. The experimental commit follows public remarks at the Open Source Summit in Prague, where Torvalds discussed his evolving view of AI tools. He told attendees that he now enjoys using AI to fill gaps, translate ideas across languages, and handle tasks outside his core expertise.
Torvalds also characterized AI as a helpful gateway drug that makes programming less intimidating for junior developers. However, he cautioned against deploying AI unthinkingly for serious tasks, warning that users must understand exactly what outcome they need.
“I think that you need to be very careful using AI when you’re doing something real and important. But I love the concept of AI as a gateway drug into programming.”
Linus Torvalds, Linux kernel creator
That pragmatism contrasts with ongoing friction over low-quality submissions. Torvalds noted that a surge of automated bug reports has placed a heavy burden on maintainers, turning security mailing lists nearly unmanageable with duplicate and obsolete vulnerability claims. He also pointed out that developers submitting AI-assisted code must review it and take full responsibility while using an Assisted-by tag.
The Noref-Filemap Branch Targets the Linux 7.4 Merge Window
Phoronix noted that while the branch targets Linux 7.3-rc6, it had not been officially merged as of publication, leaving open whether it will land during the upcoming Linux 7.4 merge window.
