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TreadMarks

TreadMarks. CS 498LVK Hassan Jafri. Agenda. The DSM Architecture The Parallel Programming Model. Programming Primitives. Shared Memory Allocation Tmk_malloc()/Tmk_free(…) Synchronization Tmk_barrier() Tmk_lock_acquire(…)/Tmk_lock_free(…) Others Tmk_startup(…), Tmk_exit(…)

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TreadMarks

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  1. TreadMarks CS 498LVK Hassan Jafri

  2. Agenda The DSM Architecture The Parallel Programming Model

  3. Programming Primitives • Shared Memory Allocation • Tmk_malloc()/Tmk_free(…) • Synchronization • Tmk_barrier() • Tmk_lock_acquire(…)/Tmk_lock_free(…) • Others • Tmk_startup(…), Tmk_exit(…) • Tmk_nprocs, Tmp_proc_id • Jacobi example

  4. DSM Architecture • Big Issues • Memory Model • Sequential Consistency (example IVY) • Total Order on all memory accesses • Read will return the last thing written • Read fault, Write faults • False sharing leading to “ping-pong” effect • HUGE OVERHEAD

  5. DSM Architecture • Big Issues • Memory Model • Release Consistency (TMK) • Latest possible time when shared memory updates mist be visible • Provide sufficient synchronization to avoid races that would make updates unnecessary until synchronization • Formally: • Acquire: Departure from barrier or lock acquire • Release: Arrival at barrier or lock release

  6. DSM Architecture • Big Issues • Memory Model • Release Consistency (TMK) • Lazy Release Consistency (TMK) • Eager Release Consistency

  7. DSM Architecture • Big Issues • Memory Model • Multiple Writer Protocol • P1 and P2 write to the same page • Page write-protected, first write access will generate fault and a twin of the page will be created • At barrier, P1 and P2 will invalidate that pages • Next time P1 and P2 access the page, diffs will be exchanged • What if P1 and P2 modify overlapping portions of the page? Learn how to program

  8. Performance Comparison • TMK vs. MPI for Jacobi • TMK vs. MPI for FFT

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