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Chapter 10 Storage Management

Chapter 10 Storage Management. Implementation details beyond programmer’s control Storage/CPU time trade-off Binding times to storage. Storage needed for code . Code User programs Library routines Storage mgt routines Static/automatic/heap allocation

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Chapter 10 Storage Management

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  1. Chapter 10 Storage Management • Implementation details beyond programmer’s control • Storage/CPU time trade-off • Binding times to storage

  2. Storage needed for code • Code • User programs • Library routines • Storage mgt routines • Static/automatic/heap allocation • Garbage collection, storage compaction • Loaders, interpreters, etc.

  3. Storage needed for data objects • programmer variables, constants • Temps for expression evaluation, functions return, parameters • Other activation record objects • Static and/or dynamic reference environment • Return point from subprogram call • Input/output buffers • Garbage collection bits, ptrs • Tables for named heap objects (Snobol4’s Central String’s Table)

  4. Routines that call for storage mgt • Subroutine entry, return • Prolog, epilog • Heap object/ class object creation, destruction • Expression evaluation • Parameter passing (specifically if expression is a parameter)

  5. Programmer control issues • Free facility (danger of dangling references) versus garbage collection overhead + delay in knowing when object has lost external path • Compare to virtual memory • Efficient allocation of storage in blocks (C) rather than according to logical need • Reuse of freed storage an issue – compaction problems

  6. Static storage management • No run-time storage mgt • Efficiency of compiler generating location for data object as offset from code section • No table or lists needed • No overlays of storage • Problem – we have a large tax table that we want to hide within a routine that computes taxes • Where is it defined? • No recursion

  7. Stack (automatic) storage management • Efficient storage mgt – stack ptr • Recursion is possible • Overlays are system controlled • Compiler generates location (l-value) as offset from start of activation record • Scope rules • (Text left this out by error)

  8. Heap storage mgt • Allocation from free list typically organized as linked list • Programmer call or creation of object • Deallocation • Programmer call or garbage collection • Is freed object placed at top of list or ordered by size? • Compaction for freed objects of different sizes • LISP list components are all the same size • Reuse • For fixed size elements, free storage is fungible • For variable size elements, do we allocate from best fit, first (random) fit

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