PostgreSQL Double Buffering: Why OS RAM and Buffer Cache Compete and How the 25% Rule Helps
By
Tiger Data (creators of TimescaleDB)
Front-window bakery material. Catches the eye, delivers the goods.
Summary
This article explains the problem of double buffering in PostgreSQL, where the OS filesystem cache and PostgreSQL's shared_buffers both cache the same data, leading to wasted RAM, increased latency, and degraded query performance. It introduces the "25% shared_buffers rule" as a guideline to mitigate this issue, explaining how to properly size the PostgreSQL buffer cache relative to available system memory to reduce competition between the two caches.
Key quotes
· 3 pulledLearn how PostgreSQL double buffering wastes RAM, increases latency, and hurts query performance — plus the 25% shared_buffers rule to fix it.
PostgreSQL's buffer cache and the OS filesystem cache often cache the same data, leading to inefficient memory usage.
The 25% shared_buffers rule is a practical guideline to balance memory allocation between PostgreSQL and the operating system.
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