The Structure of the THE Multiprogramming System p g g y THE - - PowerPoint PPT Presentation
The Structure of the THE Multiprogramming System p g g y THE (Technische Hogeschool Eindhoven) Edsger W. Dijkstra 1968 Presented by: Payal Agrawal Presented by: Payal Agrawal 1 Who is Dijkstra? Who is Dijkstra? Remember him
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Reduction of turn‐around time for programs of short duration Economic use of peripheral devices Efficient use of Memory and CPU The ability to run large flexible user programs that can i t ith h th communicate with each other Testable N d i d l i i Not designed as a multi‐user operating system
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– 32K core memory vs. 1‐2 b Gb – 512K words drum vs. 100 Gb Gb – Memory cycle time 2.5 μs
– Address size 27bits vs. 64bits L it h l – Low capacity channels supporting peripherals
printer 1 plotter and 2 teleprinter)
[Source: electrologica.nl]
printer, 1 plotter, and 2 teleprinter)
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in drum address.
“segment”
g – Core Pages (page frames) – Drum Pages (disk blocks)
to the page “physical address”
drum
Vi t l M !! Virtual Memory !!
i Vi t l Add Physical Address
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Magic Virtual Address Physical Address
– Process per program – Process per peripheral – Processes for segment controller and message interpreter g g p
effects to the internal logic of the process
processes executing independently
number of actual processors, as long as processors can it h t th i switch to the various processes
is implemented via "semaphores “ is implemented via semaphores. virtualization of the CPU!! virtualization of the CPU!!
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V " " ( i ) V: "vrygeven" (to give up)
S val = S val – 1; S.val = S.val – 1; while S.val <0 add calling process to S.list and block ; /* sleep! */}
S val = S val + 1 S.val = S.val + 1 If S.val <= 0 { remove a process Q from S.list; wakeup (Q);}
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mutex = 1;
P(mutex); critical section critical section V(mutex);
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mutex = 1; privateSemaphore = 0; p p ; P(mutex);
modify global state variables, inspect condition V(privateSemaphore); V(privateSemaphore);
V(mutex); P(privateSemaphore);
P i t S h d f C diti h i ti
– wait until condition holds before proceeding – signal when condition holds so others may proceed signal when condition holds so others may proceed
private semaphores, initialized to 0. – Max value equals 1, – Min value equals ‐1.
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privately
Homing Position: The neutral point in which all cyclic processes are when the system is at rest.
(signal) is in homing position
All ill t ll b i h i iti (
deadlock)
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EL X8 Processor Allocation
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Segment Controller
call direction
EL X8 Processor Allocation Segment Controller
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ll Message Interpreter
call direction
EL X8 Processor Allocation Segment Controller
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EL X8
buffering of input streams and unbuffering of output streams.
computer
Abstraction: Devices wrapped by buffers and abstracted to logical communication units.
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call direction
user programs
Message Interpreter Buffering I/O streams User Programs
user programs
Processor Allocation Segment Controller Message Interpreter
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EL X8
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– All the concepts are born It t k l ti ! – It took a long time! – Learnt that the society of mutually synchronized processes in time behavior can satisfy all the processes in time behavior can satisfy all the requirements
– Done in rather traditional manner – Change of specifications has been rare
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– Similar to context switching in OS
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system introduced the first forms
software‐based memory segmentation freeing programmers from being memory segmentation freeing programmers from being forced to use actual physical locations on the drum memory
A refined multiprogramming system whose implementation removes exhaustive testing
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