Lock elision for protected objects using intel transactional synchronization extensions

Abstract

Lock elision is a technique to replace coarse-grained locks by optimistic concurrent execution. In this paper, we introduce lock elision for protected objects (POs) in Ada. We employ Intel Transactional Synchronization Extensions (TSX) as the underlying hardware transactional memory facility. With TSX, a processor can detect dynamically whether tasks need to serialize through critical sections protected by locks. We adapt the GNU Ada run-time library (GNARL) to elide locks transparently from protected functions and procedures. We critically evaluate opportunities and difficulties of lock elision with protected entries. We demonstrate that lock elision can achieve significant performance improvements for a selection of three synthetic and one real-world benchmark. We show the scalability of our approach for up to 44 cores of a two-CPU, 44-core Intel E5-2699 v4 system.