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High memory usage: Bun's SQLite maps entire DB file into process address space via mmap #22429
Description
Description
Environment
- Platform: macOS ARM64
- opencode version: latest dev
- DB size: ~1.1 GB
Problem
On long-running sessions, the opencode process footprint grows to several GB. Profiling with footprint on macOS shows ~1.8 GB attributed to IOAccelerator — this is SQLite's memory-mapped pages, not actual application data.
The root cause: Bun's bundled SQLite sets a large mmap_size by default, unlike upstream SQLite which defaults to mmap_size = 0. As a result, the entire DB file is mapped into the process address space. With a 1.1 GB opencode.db, this alone accounts for ~1.8 GB of process footprint regardless of how much data is actually accessed.
Fix
Adding PRAGMA mmap_size = 0 in db.ts restores the standard SQLite default. SQLite then uses its internal page cache (already configured at ~64 MB via cache_size = -64000) instead of mmap. This caps SQLite's memory contribution at ~64 MB regardless of DB file size.
The performance impact is negligible — mmap vs read() is a sub-millisecond difference on cache misses, completely dwarfed by LLM API call latency.
I have a PR ready for this.
Plugins
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OpenCode version
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Steps to reproduce
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Screenshot and/or share link
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Operating System
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Terminal
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Activity
github-actions commentedon Apr 14, 2026
This issue might be a duplicate of existing issues. Please check:
If your issue is distinct (e.g., specifically about SQLite mmap being the root cause), please add a comment to the Memory Megathread (#20695) linking back here, as maintainers are consolidating memory reports there.
github-actions commentedon Jul 3, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.