eBPF CPU cost reduction via memoization raises memory and invalidation concerns
问题概述
High CPU cost of repeatedly opening the same files in eBPF programs; caching can cut cost by ~90% but introduces memory overhead and complex invalidation logic.
痛点标签
- CPU cost reduction claim of 90% may only apply to specific workloads
- Memory overhead of caching
- Cache invalidation challenges due to permission changes, directory moves, hard-links, deletions
- Cache size limits
- Handling of bind mounts and alternative path representations
待验证问题
- Can the 90% CPU reduction be reproduced on workloads that do not involve repeatedly opening the same file?
- What is the expected memory overhead of the cache, and is there a size limit?
- How will the cache handle invalidation events such as permission changes, directory moves, or deletions?
证据
原话
Memoization trades compute time for memory: you reduce CPU cost by 90% _at the cost_ of some memory. The author measured one, but it doesn't look like they measured the other.
原话
Seems like the 90% faster case is opening the same exact file every single time, which seems like a not super standard use case that will benefit the most from this caching.
原话
How is the cache invalidated when: The permissions change? Directories are moved? Hard-links are added? Things are deleted?
原话
How do your path-only rules handle the many approaches for loading a file but making it appear to have a different path, such as bind mounts for one example?
原话
Simple memoization yields massive wins. Had similar experience with a hot loop, sometimes the basics are just magic.
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