Definition. The Linux kernel mechanism that transparently keeps file contents in main memory to speed up repeated reads and writes. The page cache is a central layer between processes and storage and is closely intertwined with memory management, the filesystem and copy-on-write.

Why it matters. Several well-known kernel CVEs (e.g. “Dirty Pipe”, “Dirty COW”) exploited weaknesses around the page cache and COW to modify read-only files such as /etc/passwd or to escalate privileges. That is why the term keeps appearing in incident reports.

Related. Copy-on-Write (COW), Kernel LPE, CVE