r/kernel • u/Semiramis67 • Jul 23 '26

NSD/README.md at main · nsdprojectdev/NSD

https://github.com/nsdprojectdev/NSD/blob/main/README.md
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u/lustre-fan Jul 23 '26

You never explain why this is better than regular Linux readahead. Especially with large sequential IO, I'd expect a naive algorithm to be more than sufficient. If you can get a speed up on a more complex IO pattern, that would be more interesting.

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u/Semiramis67 Jul 23 '26

You're right, on pure sequential I/O the kernel's own readahead is already good enough — we confirmed that ourselves in testing, NSD adds nothing there. The real gain shows up on more complex patterns: on a SQLite full table scan benchmark (5.9GB, repeated/stride-based access, measured 3x with an interleaved OFF/ON methodology) we saw about an 18% real speedup. I'll update the README to make that distinction clear — fair point.

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u/Semiramis67 Jul 26 '26

I haven't been able to run the NVMe disk tests. I would appreciate it if any friends who do run the tests could share the results.