It’s the Software, Stupid James Larus Microsoft Research April 2005

Transactional Memory Promising abstraction for concurrent programming –CMPs bring problems to the forefront Mechanism lives in software environment –simple “hardware” transactions may not provide appropriate semantics

Example 1: Conflicting Abstractions Code

Example 1: Conflicting Abstractions Code Transactional Memory

Example 1: Conflicting Abstractions Code GC

Example 1: Conflicting Abstractions Code TM GC TM

Example 2: Nested Transactions Code LibrariesComponents

What is abstraction boundary? Can library hide internal user of concurrency? Example 2: Nested Transactions Code LibrariesComponents Libraries Code

DB Example 3: IO Code TM

Summary Not starting with a clean slate TM must work within existing environment –changes to use TM will be large –unrealistic to change everything at once