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deepmind.google·6d ago
AI Engineering
Hacker News·Jul 3·5 min read
PostgreSQL and the OOM Killer: Why You Must Use Strict Memory Overcommit
TL;DR
PostgreSQL databases are vulnerable to catastrophic failures when the Linux Out of Memory (OOM) killer terminates processes. To mitigate this, strict memory overcommit settings are recommended, which prevent excessive memory allocation.
✦ Why It Matters
Engineers should configure strict memory overcommit settings to safeguard PostgreSQL databases from OOM-related failures.
Key Takeaways
- Implement strict memory overcommit settings for PostgreSQL.
- Monitor memory usage to avoid OOM killer activation.
- Understand the implications of shared memory in PostgreSQL.
- Set memory overcommit limit to 80% plus 2 GB for stability.
Full Summary
PostgreSQL, a popular relational database, faces significant risks from the Linux OOM killer, which terminates processes when memory is overcommitted. Unlike typical applications, PostgreSQL's architecture involves a main supervisor process (postmaster) that forks backend processes for each connection, sharing memory segments.
If the OOM killer terminates a backend, it can leave shared memory in an inconsistent state, risking data corruption. To address this, the team implemented strict memory overcommit settings, ensuring that memory allocation does not exceed physical limits.
This approach minimizes the risk of OOM kills affecting multiple connections and triggering crash recovery. Their analysis revealed that maintaining an overcommit limit of 80% plus an additional 2 GB is optimal for performance and stability.
These findings underscore the importance of proper memory management in database systems.