Concurrent Systems II - Bad Request - Trinity College Dublin

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Relocation and non-contiguity 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4 5 5 5 5 5 5 6 6 6 6 6 6 7 7 7 7 7 7 8 8 8 8 8 8 9 9 9 9 9 9 10 10 10 10 10 10 11 11 11 11 11 11 12 12 12 12 12 12 13 13 13 13 13 13 14 14 14 14 14 14 Load A Load B Load C Swap out B Load D 156 Trinity College Dublin © Mike Brady 2007–2009
Virtual memory • Give each process its own virtual address space ◾ Divide the space into fixed-size pages (e.g. 4KB or 212B) • Programs refer to addresses in their own virtual memory space – virtual addresses • “On-the-fly” conversion of virtual addresses into physical addresses, which are applied to physical memory 32 bit address 20 bits 12 bits Virtual address Physical address virtual page number translated by MMU physical page frame number page offset page offset unchanged Trinity College Dublin © Mike Brady 2007–2009
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Concurrent Systems II (CS3D4/CS3BA2
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POSIX Threads • POSIX Threads aka
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Six Separate Threads Master Thread
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Where… • ‘thread’ is the ID
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Hello World -- Creating Threads int
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Hello World -- Thread Function void
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Wilde/Stoker/Ubuntu h-3.1$ cc -lpth
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Interaction • No thread interacti
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Interactions & Dependencies • Int
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…to do Parallel Programming • H
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Hardware Main Memory Level 2 Cache
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Shared Memory Machine • Each proc
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Concurrent Program • A Concurrent
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Communication • A parallel progra
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1 - Flow Dependence S1: write to lo
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3 - Output Dependence S1: write to
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Dependence in Loops j k k i 1 2 j 5
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How can we transform it? • We can
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Issues: • The variable sum, as wr
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Summarising: • We could paralleli
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Example • Sample function: y = 0.
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Synchronisation • We’ve looked
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Shared Variable S: Thread 1 after T
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Mutual Exclusion in pthreads. • M
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Shared Variable S Protected by Mute
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Lock and Unlock Mutex • pthread_m
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} /********** Critical Section ****
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Problem Tutorial • The transpose
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Producers and Consumers • Essenti
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Condition Variables (2) • Dramati
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From Thread U’s POV (2) • If C
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From Thread U’s POV (4) • Acqui
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Thread S (2) • Acquire Mutex M
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Semaphores • Computer Semaphores
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Semaphore Consumer ◾Acquire Mutex
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Semaphores (3) • Useful for count
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Sample Solution for ∏ • Calcula
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unsigned long long clock_cycles() {
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The Challenge of Concurrency • Co
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Concurrent Execution • A concurre
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Notation Trivial Concurrent Program
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Trivial Concurrent Program p1: n
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Example — Jumping Frogs • A fro
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If the frogs can only move “forwa
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State Diagrams for Processes • A
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Book Reference Principles of concur
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Correctness • (Correctness in Seq
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Using State machines • We can des
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The Critical Section Problem (2)
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Observations & Implications • Rem
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Simplify Critical Section Problem i
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State Transitions r1,s1,1 r1: await
Page 105 and 106: Deadlock Free? • Deadlock Free: I
Page 107 and 108: Scorecard Mutual Exclusion Deadlock
Page 109 and 110: Attempt #2 Critical Section Problem
Page 111 and 112: Attempt #2 Fails… • Attempt 2 f
Page 113 and 114: Attempt #3 Critical Section Problem
Page 117 and 118: Attempt #4 loop forever Critical Se
Page 121 and 122: Attempt #5, derived from #4 Critica
Page 123 and 124: Verification of concurrent programs
Page 125 and 126: A quick overview of some mathematic
Page 127 and 128: A quick overview of some mathematic
Page 129 and 130: Proving correctness by induction
Page 131 and 132: A quick overview of some temporal l
Page 133 and 134: A quick overview of some temporal l
Page 135 and 136: Temporal logic at work • Consider
Page 137 and 138: Promela • Promela [Protocol/Proce
Page 139 and 140: Process (2) • A process type (pro
Page 141 and 142: SPIN Hello World Example SPIN = Sim
Page 143 and 144: Promela Variables (2) • Arrays
Page 145 and 146: Statements (2) • The skip stateme
Page 147 and 148: If Statement if :: (n % 2 != 0) ->
Page 149 and 150: Atomic Statement atomic { stat1; st
Page 151 and 152: Process Execution / Evaluation Sema
Page 153 and 154: The Closed World Assumption • The
Page 155: Process memory management • In a
Page 159 and 160: Virtual memory 0 0 process 1 2 32 0
Page 161 and 162: Memory management requirements and
Page 163 and 164: E.g. Virtual memory implementation
Page 165 and 166: Multi-level page tables Virtual add
Page 167 and 168: Typical process memory layout memor
Page 169 and 170: Translation look aside buffer • E
Page 171 and 172: Page fault handling Start Access pa
Page 173 and 174: Fetch policy • When should a page
Page 175 and 176: Page replacement policy • A page
Page 177 and 178: Page replacement policy • First-I
Page 179 and 180: Clock Algorithm 179 Trinity College
Page 181 and 182: Resident set management • Variabl
Page 183 and 184: Resident set management Local Repla
Page 185 and 186: Resident set management Δ Working
Page 187 and 188: Resident set management 187 Trinity
Page 189 and 190: Cleaning policy • Page buffering
Page 191 and 192: Load control • We can use a few d
Page 193 and 194: Process state transitions • Proce
Page 195 and 196: Preemptive and nonpreemptive schedu
Page 197 and 198: Scheduling algorithms • First-Com
Page 199 and 200: Scheduling algorithms • Shortest-
Page 201 and 202: Scheduling algorithms • Priority
Page 203 and 204: Scheduling algorithms • Round-Rob
Page 205 and 206: Example Process Arrival Time Next B
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Scheduling algorithms • Multi-lev
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Scheduling algorithms • Multi-lev
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Multi-processor scheduling • Flyn
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Layered file I/O (1) Application Di
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Disk access • Disks are slow ◾
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Disk scheduling • So, the order i
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Disk scheduling algorithms (2) •
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Concurrent Systems II - Bad Request - Trinity College Dublin

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