Torvalds Uses Claude Code for Unmerged Linux Page-Cache Patches

Linus Torvalds used Claude Code to draft unmerged Linux patches that cut page-cache reference contention on small cached reads.

Linus Torvalds said Anthropic’s Claude Code, under his supervision, drafted an unmerged eight-patch Linux series, “mm: read from the page cache without folio references,” plus tests and notes aimed at page-cache scalability. The work uses RCU so readers can copy cached file data without taking folio references, waiting for a grace period before reusing removed page-cache memory. On a Core i7-8565U, one report said folio reference-count contention accounted for 99.92% of cross-core load HITMs in an eight-thread synthetic test; a later report, describing a four-core Intel laptop and ext4 with some hardening disabled, said throughput rose from about 9.9–10.4 million to roughly 30–33 million 16-byte cached reads per second. Both sources say the series is not merged and still needs broader human review. Reviewers found a race in filemap_read_rcu_batch() that could expose never-written data, while Torvalds said the benchmark is narrow, memory accounting under pressure is unresolved, and KASAN, lockdep, other architectures, and several stress cases were not tested. No CVE or exploitation was reported, and the patches were described as sitting on Linux 7.3-rc6 in Torvalds’ repository.

• Unmerged eight-patch series “mm: read from the page cache without folio references” sits on Linux 7.3-rc6 in Torvalds’ repository.
• Claude Code, under Linus Torvalds’ direction, drafted the patches plus tests, review notes, and a technical write-up.
• On a Core i7-8565U, folio reference-count contention accounted for 99.92% of cross-core load HITMs in an eight-thread synthetic test.
• A later report said a four-core Intel laptop rose from about 9.9–10.4 million to roughly 30–33 million 16-byte cached reads per second on ext4 with some hardening disabled.
• RCU delays reuse of removed page-cache memory so readers can copy cached data without taking folio references.
• Reviewers found a race in filemap_read_rcu_batch() that could expose never-written file data; no CVE or exploitation was reported.
• Memory accounting under pressure remains unresolved; KASAN, lockdep, other architectures, and several stress cases were not tested.