minor page fault
also: soft page fault
A page fault that is resolved by retrieving a page from RAM (such as from the filesystem cache) rather than from disk, resulting in minimal performance impact.
A minor page fault (also called a soft page fault) occurs when a program accesses memory that isn't currently mapped into its page table, but the data already exists in RAM—typically in the kernel's filesystem cache or shared memory regions.
When a minor page fault happens, the kernel simply updates the process's page table to point to the existing page in memory, without needing to perform slow disk I/O. This is much faster than a major page fault, which requires reading from disk.
Example: A program reads a file for the second time. The first read caused a major page fault (disk to RAM), but the kernel cached that file. The second read triggers minor page faults because the kernel retrieves pages from the cache instead of re-reading the disk.
You can observe minor and major page faults using ps, /proc/[pid]/stat, or tools like time -v, which report them as minflt and majflt respectively.