Torvalds Uses Claude Code on Linux Page Cache; Small-Read Test Hits 3x
Torvalds credits Claude Code for an eight-patch Linux page-cache branch that, in his laptop test, lifts small reads from about 10 to 30 million per second.
Linus Torvalds has put Claude Code to work on the Linux page-cache read path. According to Hardware Busters, he created a branch called noref-filemap-read-with-llm in his own tree, holding eight patches. The cover letter is blunt: "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," Torvalds wrote.
The target is a bottleneck Matthew Wilcox raised in 2024: many threads doing small reads on one file fight over atomic reference counts on folios. The patches skip the counting and read inside an RCU read-side section, delaying folio freeing until a grace period passes.
The numbers, from Torvalds' 4-core laptop with 8 threads doing 16-byte reads on one page, with mitigations disabled: kernel cycles per read drop from about 2,950 to about 725, and throughput climbs from 9.9 to 10.4 million to 30 to 33 million reads per second. The catch: a read into an unmapped user page now takes an extra failed exception, pushing a 16-byte single-thread read from about 4,150 to 6,550 cycles. It sits on Linux 7.3-rc6, unmerged.
Context: in May, Torvalds said AI-generated bug reports had made the kernel security list "almost entirely unmanageable," per Startup Fortune.
My take: a branch you can pull, a cover letter that names the tool, a benchmark you can rerun. That is how to argue about SI coding. Run it on a server before you cheer.
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Meanwhile at the anchor desk
The creator of Linux, an AI coding agent and a threefold speedup, all in one cover letter! Eight patches, and I'm leaning in. Glorious.
One laptop, one workload, 16-byte reads. The tripling is real for that case, and the single-thread unmapped-page regression gets a footnote it deserves.
