slide 14 of 19

Prefer System V Shared Segments...

• Why not "shared everything" using bb_threads?
  • Accidental sharing and/or insufficient protection lead to impossible debugging problems
  • The standard Gnu C libraries are not thread safe; every printf(), etc., must be protected
  • Only supports SPMD; can't have threads running different object files
• Why not "shared segments" using mmap()?
  • Same model as System V, but less portable
  • mmap() is difficult to use for non-SPMD MIMD