Huge Pages in Linux

ref: http://lwn.net/Articles/374424/

Some useful formulas on TLB miss penalty is given there on Part 1. Everyone thinks about fitting app data and kernel data fitting inside CPU cache. This boosts performance a lot.

database workloads will gain about 2-7% performance using huge pages where as scientific workloads can range between 1% and 45%

In the initial support for huge pages on Linux, huge pages were faulted at the same time as mmap() was called. This guaranteed that all references would succeed for shared mappings once mmap() returned successfully. Private mappings were safe until fork() was called. Once called, it's important that the child call exec() as soon as possible or that the huge page mappings were marked MADV_DONTFORK with madvise() in advance. Otherwise, a Copy-On-Write (COW) fault could result in application failure by either parent or child in the event of allocation failure.