Memory Management I

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Memory Management I
Written Assignment 2 due Systems Assignment 1
returned Systems Assignment 2 due next time
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Memory Management I
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Memory Management I
III. Memory Management II

• manage the scarce resource of memory

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Memory Management I
all previous MMS required

• - entire program in RAM
• - program in contiguous RAM
• - entire program to remain in RAM

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Memory Management I
A. Paged memory allocation scheme

• concept which is part of all current MMS

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Memory Management I
A. Paged memory allocation scheme

• removes the requirement that entire program must
  be in contiguous RAM

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Memory Management I
A. Paged memory allocation scheme

• 1. Programs (jobs) are divided into equal-size
  pages

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Memory Management I
OS
Program
Disc storage
RAM memory
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Memory Management I
2. Tradeoffs

• a. adv - doesnt require contiguous
  RAMefficient memory usage

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Memory Management I
2. Tradeoffs

• b. dis - additional OS work system overhead

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Memory Management I
2. Tradeoffs

• OS needs a PMTfig 3.1

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Memory Management I
3. OS implementation

• a. Job Table
• b. Page Map Table
• c. Memory Map Table
• d. address resolution

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another classic company
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Memory Management I
B. Demand Paging MMS

• first virtual memory MMS

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Memory Management I
B. Demand Paging MMS

• 1. only those necessary pages are loaded for
  execution

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Memory Management I
B. Demand Paging MMS

• viable scheme due to locality of reference

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Memory Management I
2. Tradeoffs

• a. adv - virtual memory

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Memory Management I
2. Tradeoffs

• b. dis - additional OS work system overhead
• ex thrashing

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Memory Management I
3. OS implementation

• a. expanded PMT

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Systems Assignment 1
Bare Bones Code Set fso CreateObject("Scripti
ng.FileSystemObject") Set drv
fso.GetDrive(C) Wscript.Echo Total Size
drv.TotalSize vbCrLf Free Space
drv.FreeSpace
Professional Programming Practice
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Systems Assignment 1
' Gary Locklair ' CSC350 - Systems Assignment
1 ' Windows Scripting Host ' VBscript ' ' Script
will determine and display Total Size and Free
Space ' available on drive C ' ' explicitly
declare varibles with Dim ' Dim fso, drv, msg,
drvPath ' ' hardcode drive path ' drvPath
"C\" ' ' fso will be the object instance of the
FileSystemObject class ' Scripting is the "type
library" CreateObject is a method ' Set fso
CreateObject("Scripting.FileSystemObject") ' '
note the use of object.method syntax ' Set drv
fso.GetDrive(fso.GetDriveName(drvPath))
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Systems Assignment 1
' ' build up msg string for output ' msg
"Drive " UCase(drvPath) " - " msg msg
drv.VolumeName " " ' ' Note formatting not
necessary for this assignment ' msg msg
"Total Space " FormatNumber(drv.TotalSize /
1024, 0) msg msg " KB" " " msg msg
"Free Space " FormatNumber(drv.FreeSpace /
1024, 0) msg msg " KB" " " ' ' Note
output will appear in two separate, successive
windows ' Wscript.echo msg Wscript.echo "End of
Output"
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