1. Symmetric Multiprocessing (SMP) REVIEW

2. Categories of Computer Systems • Single Instruction Single Data (SISD) • single processor executes a single instruction stream to operate on data stored in a single memory • Single Instruction Multiple Data (SIMD) • one instruction is executed on a different set of data by the different processors

3. Categories of Computer Systems • Multiple Instruction Single Data (MISD) • a sequence of data is transmitted to a set of processors, each of which executes a different instruction sequence. Never implemented • Multiple Instruction Multiple Data (MIMD) • a set of processors simultaneously execute different instruction sequences on different data sets

4. Parallel Processor Architecture MIMD Distributed memory (self-contained computers) Shared memory multiprocessor Clusters Symmetric multiprocessors (SMP) Master/Slave

5. Symmetric Multiprocessing • Kernel can execute on any processor • Typically each processor does self-scheduling from the pool of available process or threads • portions of the kernel can execute in parallel in different processors

6. Symmetric Multiprocessor Organization Processor Processor . . . Processor Cache Cache Cache Main Memory I/O Subsystem

7. Multiprocessor OS requirements • Must provide functionality of a multiprogramming OS plus additional features to support multiple processors • Simultaneous concurrent processes or threads: kernel routines need to be reentrant • Scheduling done by any processor, can create conflicts. • Synchronization through locks is required. • Memory management needs to be coordinated in the different processors • Much more complex than just multiprogramming OS.