Modal intern's EROFS work speeds agentic workloads 4x and directory traversal 12x on gVisor

charles_irl · x · 2026-09-08

A Modal intern rebuilt the container filesystem path on gVisor using a custom lazily-served EROFS image, so filesystem ops resolve inside the sentry instead of traversing the host stack. Result: up to 4x speedup on agentic workloads and 12x faster directory traversal, while keeping lazy-loading for fast cold starts. The post explains container image structure, lazy loading, and how the EROFS driver plugs into gVisor.

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