SAW: Java Synchronization Selection from Lock or Software Transactional Memory

Abstract

To rewrite a sequential program into a concurrent one, the programmer has to enforce atomic execution of a sequence of accesses to shared memory to avoid unexpected inconsistency. There are two means of enforcing this atomicity: one is the use of lock-based synchronization and the other is the use of software transactional memory (STM). However, it is difficult to predict which one is more suitable for an application than the other without trying both mechanisms because their performance heavily depends on the application. We have developed a system named SAW that decouples the synchronization mechanism from the application logic of a Java program and enables the programmer to statically select a suitable synchronization mechanism from a lock or an STM. We introduce annotations to specify critical sections and shared objects. In accordance with the annotated source program and the programmer's choice of a synchronization mechanism, SAW generates aspects representing the synchronization processing. By comparing the rewriting cost using SAW and that using individual synchronization mechanism directly, we show that SAW relieves the programmer's burden. Through several benchmarks, we demonstrate that SAW is an effective way of switching synchronization mechanisms according to the characteristics of each application.

A Lock Free Approach To Parallelize The Cellular Potts Model: Application To Ductal Carcinoma In Situ

“…Nor is it especially difficult to have threads that remain at livelock when they continually fail to achieve the lock provided by a particular synchronization point. Much has been written and researched on how to avoid all of the above [ 21 ], [ 22 ], [ 23 ], [ 24 ], and numerous are the proposed formal techniques to avoid committing the typologies of failures described. Notwithstanding the foregoing, the control of concurrency remains a complex matter, where producing a clean code is not within everyone’s reach.…”

“…The whole process is graphically presented in Figure 3 . There are multiple implementations of STM for Java [ 11 ], [ 24 ]. With STM, programmers only need to delimit in their code the access to shared data, and wrap them within a transaction.…”

“…Any other thread, attempting to change the identity in turn, will see the updated status. Since there are no blocks, the concurrency is in principle greater [ 11 ], [ 21 ], [ 22 ], [ 23 ], [ 24 ]. It is enough to have the guarantee that we offer to the threads a consistent vision of the world, and the truth is that with Clojure, it is not necessary for us to worry about doing so.…”

Subobject Transactional Memory

“…SAW [20] is a Java library that adds synchronization to existing classes through aspect weaving. Classes and transactional methods are marked with @shared and @atomic annotations.…”