Concurrent Systems II - Bad Request - Trinity College Dublin

More documents

Recommendations

Info

Memory-management: the OS perspective • What are we interested in from an OS perspective? ◾ Page fault handling • The goal of the operating system is to attempt to minimise the occurrence of page faults, which are expensive ◾ Need to decide which physical memory page to use ◾ Need to perform I/O ◾ Another process needs to be scheduled to run during the I/O, resulting in a context switch • We will look at several policies used by the OS to perform memory management ◾ The key questions are: • When should a page be loaded? • Where (in physical memory) should it be loaded? 172 Trinity College Dublin © Mike Brady 2007–2009
Fetch policy • When should a page be loaded? ◾ Two alternatives • Demand Paging ◾ Pages are loaded into memory only when they are first referenced ◾ When a process is started, there will be a number of page faults in quick succession ◾ Locality of reference: over a short period of time, most memory references are to a small number of pages • The pages references changed relatively slowly over time • Prepaging (performed in addition to demand paging) ◾ Takes advantage of the characteristics of disk devices • Seek times and rotational latency ◾ If a number of pages are contiguous in secondary storage, it is more efficient to load the contiguous pages, even though they haven’t been referenced yet 173 Trinity College Dublin © Mike Brady 2007–2009
Page 1 and 2:
Concurrent Systems II (CS3D4/CS3BA2
Page 3 and 4:
POSIX Threads • POSIX Threads aka
Page 5 and 6:
Six Separate Threads Master Thread
Page 7 and 8:
Where… • ‘thread’ is the ID
Page 9 and 10:
Hello World -- Creating Threads int
Page 11 and 12:
Hello World -- Thread Function void
Page 13 and 14:
Wilde/Stoker/Ubuntu h-3.1$ cc -lpth
Page 15 and 16:
Interaction • No thread interacti
Page 17 and 18:
Interactions & Dependencies • Int
Page 19 and 20:
…to do Parallel Programming • H
Page 21 and 22:
Hardware Main Memory Level 2 Cache
Page 23 and 24:
Shared Memory Machine • Each proc
Page 25 and 26:
Concurrent Program • A Concurrent
Page 27 and 28:
Communication • A parallel progra
Page 29 and 30:
1 - Flow Dependence S1: write to lo
Page 31 and 32:
3 - Output Dependence S1: write to
Page 33 and 34:
Dependence in Loops j k k i 1 2 j 5
Page 35 and 36:
How can we transform it? • We can
Page 37 and 38:
Issues: • The variable sum, as wr
Page 39 and 40:
Summarising: • We could paralleli
Page 41 and 42:
Example • Sample function: y = 0.
Page 43 and 44:
Synchronisation • We’ve looked
Page 45 and 46:
Shared Variable S: Thread 1 after T
Page 47 and 48:
Mutual Exclusion in pthreads. • M
Page 49 and 50:
Shared Variable S Protected by Mute
Page 51 and 52:
Lock and Unlock Mutex • pthread_m
Page 53 and 54:
} /********** Critical Section ****
Page 55 and 56:
Problem Tutorial • The transpose
Page 57 and 58:
Producers and Consumers • Essenti
Page 59 and 60:
Condition Variables (2) • Dramati
Page 61 and 62:
From Thread U’s POV (2) • If C
Page 63 and 64:
From Thread U’s POV (4) • Acqui
Page 65 and 66:
Thread S (2) • Acquire Mutex M
Page 67 and 68:
Semaphores • Computer Semaphores
Page 69 and 70:
Semaphore Consumer ◾Acquire Mutex
Page 71 and 72:
Semaphores (3) • Useful for count
Page 73 and 74:
Sample Solution for ∏ • Calcula
Page 75 and 76:
unsigned long long clock_cycles() {
Page 77 and 78:
The Challenge of Concurrency • Co
Page 79 and 80:
Concurrent Execution • A concurre
Page 81 and 82:
Notation Trivial Concurrent Program
Page 83 and 84:
Trivial Concurrent Program p1: n
Page 85 and 86:
Example — Jumping Frogs • A fro
Page 87 and 88:
If the frogs can only move “forwa
Page 89 and 90:
State Diagrams for Processes • A
Page 91 and 92:
Book Reference Principles of concur
Page 93 and 94:
Correctness • (Correctness in Seq
Page 95 and 96:
Using State machines • We can des
Page 97 and 98:
The Critical Section Problem (2)
Page 99 and 100:
Observations & Implications • Rem
Page 101 and 102:
Simplify Critical Section Problem i
Page 103 and 104:
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 115 and 116:
Page 117 and 118:
Attempt #4 loop forever Critical Se
Page 119 and 120:
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 and 156: Process memory management • In a
Page 157 and 158: Virtual memory • Give each proces
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: Page fault handling Start Access pa
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
Page 207 and 208: Scheduling algorithms • Multi-lev
Page 209 and 210: Scheduling algorithms • Multi-lev
Page 211 and 212: Multi-processor scheduling • Flyn
Page 213 and 214: Layered file I/O (1) Application Di
Page 215 and 216: Disk access • Disks are slow ◾
Page 217 and 218: Disk scheduling • So, the order i
Page 219 and 220: Disk scheduling algorithms (2) •
show all

Concurrent Systems II - Bad Request - Trinity College Dublin

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?