FFS optimizations with dirhash, as blogged by rsadowski@

Contributed by Peter N. M. Hansteen on 2025-06-08 from the Hash for FFS sake dept.

Rafael Sadowski (rsadowski@), OpenBSD developer and prolific blogger, has been looking into file system performance optimizations on our favorite operating system, and is now sharing his tips and tricks in FFS optimizations with dirhash on his blog.

He leads in with a TL;DR:

tl;dr
Consider playing with sysctl vfs.ffs.dirhash_maxmem to increase the maximum dirhash cache.

That said, it is worth your time to read the whole thing!

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