Conviva Replaced mmap with io_uring in Its Rust Query Engine — and It Got Slower

blaizedsouza · x · 2026-09-04

Conviva engineer Evan Chan published a two-part blog on replacing mmap with iouring in the company's Rust query engine.
mmap initially fit perfectly: Arrow IPC's layout supports zero-copy random access, and mmap lazily reads huge numbers of files without manual memory management.
In production under real concurrent query loads, mmap became a serious problem (page faults, page-cache contention).
The team switched to iouring for async I/O — and it got slower. The series dissects why, and doubles as the basis for his P99 CONF talk.

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