Post Syndicated from corbet original https://lwn.net/Articles/1100449/

At the recently concluded Maintainers
Summit, Linus Torvalds said that he had been using a large language
model to work on a patch series addressing a longstanding problem; he has
now posted
that series for review.

The fairly short series of ten patches basically enhances folio
lookup by noticing when folios are hot, and setting a “delay
releasing this folio until after a RCU period”, and then using that
RCU delay it does not just the folio lookup itself under RCU (which
we’ve done forever), but also the actual folio data accesses
themselves under RCU. No refcount taking needed for the fastpath
where we can just read the data from the folio entirely in an
RCU-protected region when the user copy doesn’t cause page faults.

The end result is an order-of-magnitude speedup for a read()-heavy
benchmark. Review has already identified a race
condition in the code, though, so further work will be needed.