Memory Management

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Memory Management
Kathryn McKinley University of Texas at Austin
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About me
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Software for Software
Program
Compiler translates human format to computer
format
Executable
Computer
Runtime System Software
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Whats Inside?
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IBM Power4 Microprocessor
Only 12 of Non-Cache, Non-TLB Core Area is
Execution Units
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Memory System Organization
Registers
Instruction Cache
CPU Central Processing Unit
Level 2 Cache
Data Cache
Memory
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Software for Software
Program
Compiler translates human format to computer
format
Executable
Computer
Runtime System Software
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Eating

• Do forever
• Prepare meal
• Select plates, bowls, silverware
• Serve food Eat
• You wash your dishes
• Explicit Memory Management

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Select Plates, Bowls, Silverware
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Select Plates, Bowls, Silverware
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Explicit Memory ManagementHand Wash Dishes
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Explicit Memory ManagementHandwashing
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Explicit Memory ManagementHand Wash Dishes
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Explicit Memory ManagementHandwashing
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Explicit Memory ManagementHand Wash Dishes
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Dish Washer Automatic Memory ManagementGarbage
Collection

• Do forever
• Prepare meal
• Select plates, bowls, silverware
• Serve food Eat
• Dad put dishes in dishwasher
• Dad checks if dishwasher full or
• Out of plates, bowls or silverware
• Dad runs dishwasher

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Select Plates, Bowls, Silverware
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Select Plates, Bowls, Silverware
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Dad Runs Dish Washer Puts Up Dishes
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Computer Resources
Page
Memory
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Mapping Dishes to Computer Resources
Data Structure Declarations
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Contiguous Allocation
New (Plate1)
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Contiguous Allocation
New (Plate1) New (Plate2) New (Bowl1) New
(Fork1) New (Fork2) New (Spoon1)
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Contiguous Allocation
etc.
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Explicit Memory ManagementFree with Continuous
Allocation
Free (Bowl3)
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Free with Contiguous Allocation
Free (Bowl3) Free (Spoon1)
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Garbage Collection(Automatic Memory Management)
with Contiguous Allocation
Wait longer
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Garbage Collection with Contiguous Allocation
L
L
Find live objects L
L
L
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Garbage Collection with Contiguous Allocation
Find live objects L Copy live objects to new area
L
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Garbage Collection with Contiguous Allocation
Find live objects L Copy live objects to new
area Reclaim old space
L
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Garbage Collection with Contiguous Allocation
Find live objects L Copy them to new
area Reclaim old space Allocate into new space
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Allocation withSize-Class Free-Lists
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Explicit Memory ManagementFree with
Size-Classes Free-Lists
Free (Bowl3) Free (Spoon1)
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Memory Management

• All memory management uses one of these two basic
  mechanisms
• Contiguous allocation
• Size-Class Free-Lists
• Classic Computer Science Problem in Space-Time
  tradeoff

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Other Key Ideas in Memory Management

• Locality
• Incrementality
• Generational behavior
• Older-first behavior
• My research group introduced this one!

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Questions?