04~Chapter_04 - Foundations of Shared Memory Companion...

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Unformatted text preview: Foundations of Shared Memory Companion slides for The Art of Multiprocessor Programming by Maurice Herlihy & Nir Shavit 2007 Herlihy & Shavit 2 Last Lecture Defined concurrent objects using linearizability and sequential consistency Fact : implemented linearizable objects (Two thread FIFO Queue) in read-write memory without mutual exclusion Fact : hardware does not provide linearizable read- write memory 2007 Herlihy & Shavit 3 Fundamentals What is the weakest form of communication that supports mutual exclusion? What is the weakest shared object that allows shared-memory computation? 2007 Herlihy & Shavit 4 Alan Turing Helped us understand what is and is not computable on a sequential machine. Still best model available 2007 Herlihy & Shavit 5 1 1 1 1 Turing Machine Reads and Writes Infinite tape Finite State Controller 2007 Herlihy & Shavit 6 Turing Computability Mathematical model of computation What is (and is not) computable Efficiency (mostly) irrelevant 1 1 1 1 2007 Herlihy & Shavit 7 Shared-Memory Computability? Mathematical model of concurrent computation What is (and is not) concurrently computable Efficiency (mostly) irrelevant 10011 Shared Memory 2007 Herlihy & Shavit 8 Foundations of Shared Memory To understand modern multiprocessors we need to ask some basic questions 2007 Herlihy & Shavit 9 Foundations of Shared Memory To understand modern multiprocessors we need to ask some basic questions What is the weakest useful form of shared memory? 2007 Herlihy & Shavit 10 Foundations of Shared Memory To understand modern multiprocessors we need to ask some basic questions What is the weakest useful form of shared memory? What can it do? 2007 Herlihy & Shavit 11 Foundations of Shared Memory To understand modern multiprocessors we need to ask some basic questions What is the weakest useful form of shared memory? What can it do? What cant it do? 2007 Herlihy & Shavit 12 Register 10011 Holds a (binary) value * * A memory location: name is historical 2007 Herlihy & Shavit 13 Register Can be read 10011 10011 2007 Herlihy & Shavit 14 Register Can be written 10011 01100 2007 Herlihy & Shavit 15 public interface Register<T> { public T read(); public void write(T v); } Registers 2007 Herlihy & Shavit 16 public interface Register <T> { public T read(); public void write( T v ); } Registers Type of register (usually Boolean or m-bit Integer) 2007 Herlihy & Shavit 17 10011 Single-Reader/Single-Writer Register 01100 10011 2007 Herlihy & Shavit 18 10011 Multi-Reader/Single-Writer Register 01100 10011 2007 Herlihy & Shavit 19 mumble mumble 11011 Multi-Reader/Multi-Writer Register mumble 10011 10011 10011 01010 2007 Herlihy & Shavit...
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04~Chapter_04 - Foundations of Shared Memory Companion...

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