Addressing Contention: Fine-Grained Locking

• Decompose the Giant lock into a series of smaller locks that contend less

  • Typically over “code” or “data”
  • E.g., scheduler lock permits user context switching without waiting on the file system
  • Details vary greatly by OS

• Iterative approach

  • Typically begin with scheduler lock
  • Dependency locking such as memory allocation
  • Some high level subsystem locks
  • Then data-based locking
  • Drive granularity based on observed contention