Introduction_to_Garbage_Collection_I_Why_is_Automatic_GC_Important_and_Hard_II_Reference_Co外文翻译.pdf

Lecture 12 Introduction to Garbage Collection I Why is Automatic GC Important and Hard? II Reference Counting III Basic Trace-Based GC Readings: Chapter 7.4-7.6.4 Advanced Compilers M. Lam I. Memory Management, manual or automatic • Memory management: reclaim unused memory space • Why do we care about memory management? • When do we care about memory management? • What is perfect memory management? Advanced Compilers 2 L12: Garbage Collection Why Automatic Memory Management? • Perfect live dead not deleted −−− deleted −−− • Manual management live dead not deleted deleted • Assume for now the target language is Java Advanced Compilers 3 L12: Garbage Collection What is Garbage? Advanced Compilers 4 L12: Garbage Collection When is an Object not Reachable? • Mutator (the program) • New / malloc: (creates objects) • Store p in a pointer variable or field in an object • Load p • Procedure calls • Important property • once an object becomes unreachable, stays unreachable! Advanced Compilers