Shared-memory multiporcessor:

  • SMP(symmetric multiprocessors / centralized shared-memeory multiprocessor) => UMA(uniform memory access)
x
  • DSM(distributed shard memory) => NUMA(nonuniform memory access)
x

Coherence vs Consistency

  • Coherence Defines the behavior of reads and writes to the same memory location.
  • Consistency defines the behavior of reads and writes with respect to accesses to other memory locations.

Coherence Protocols

  • Snooping
    • MSI

    • MESI
    • MOESI
  • Directory based

Snooping coherence protocol example

  • State(MSI):
    • Invalid
    • Shared
    • Modified
x
x
x

Directory-based coherence protocol example

x
x

Memory consistency models

  • Sequential consistency
  • Processor consistency
  • Relaxed consistency

Synchronization

  • Automic operation: single uninterruptible instruction
  • Conditional store: piar of instructions (load locked / store conditional)

Reference:

Computer Architecture: A Quantitative Approach 5th Edition
Intel i7-4770 (Haswell) performance
Understanding CPU caching and performance
Computer memory history