An Innovative Approach for Achieving Composability in Concurrent Systems using Multi-Version Object Based STMs

In the modern era of multicore processors, utilizing multiple cores properly is a tedious job. Synchronization and communication among processors involve high cost. Software transaction memory systems (STMs) addresses this issues and provide better concurrency in which programmer need not have to worry about consistency issues. Several big-data applications which deal large amounts of data can benefit from Transactional Memory Systems. In this paper, we introduce a new STM system as multi-version object based STM (MV-OSTM) which is the fusion of object based STM with multiple versions. As the name suggests MV-OSTM, works on a higher level and keeping the multiple versions corresponding to each key. Presently, we have developed MV-OSTM with the unlimited number of versions corresponding to each key. To overcome traversal overhead, it performs the garbage collection method to delete the unwanted versions corresponding to the key. It provides greater concurrency while reducing the number of aborts. It ensures composability by making the transaction as atomic. In the proposed algorithm, k is the input parameter and the value of it will be decided by the programmer and depends on the application. Programmer can tune the value of k from 1 to∞. If k equal to 1 then it will boil down to single version object based STM (OSTM) and if k equal to ∞ then it will be equivalent to multi-version OSTM with∞ versions. MV-OSTM satisfies correctness-criteria as opacity. For a given version order of keys, if any history H generated by MV-OSTM produces acyclic graph then H is opaque. The progress condition of the proposed MV-OSTM is multi-version permissiveness or mv-permissiveness which never aborts a transaction which is having return-value method only. To the best of our knowledge, this is the first work to explore the idea of using multiple versions in OSTMs to achieve greater concurrency.