Filesystem page cache
Also known as OS page cache, warm filesystem cache
In plain English
The filesystem page cache keeps recently accessed file data in RAM so later reads can avoid the storage device.
Technical definition
The filesystem page cache is operating-system-managed memory holding file data, including resident pages accessed through file-backed mappings.
Engineering details
A warm Engram mapping may serve its requested rows entirely from RAM. Under memory pressure the operating system can reclaim file-backed pages, making later accesses depend on storage again. The table being backed by SSD therefore does not prove that each lookup reads the SSD.
Why it matters
Cache state changes the meaning of storage benchmarks. It is necessary to distinguish logical reads from physical device I/O and to account for resident file pages when claiming host-memory savings.
How to read it in InferenceX
In the article, a warm cache removes SSD reads but leaves CPU coordination, row gathering, and transfers in the unoptimized path. The measured result supports a comparison of complete serving implementations, not an isolated claim about the latency of NAND flash.