Using program metadata to support SDT in object-oriented applications

Abstract

Software dynamic translation (SDT) is a powerful technology that enables software malleability and adaptivity at the instruction level by providing facilities for run-time monitoring and code modification. SDT has been used as the basis for many valuable tools, including dynamic optimizers, profilers, security policy enforcement, and binary translation to name a few. However, modern object-oriented programming techniques and their implementations (e.g., virtual functions, exceptions, dynamic code, etc.) pose unique challenges to high performing SDT systems. In this paper, we present Metaman, a generalized program metadata manager that stores and manages program information so that it can be efficiently accessed by emerging SDT systems to improve overall runtime performance of a managed executable. Using the information collected by Metaman, the run-time performance of an existing SDT system was improved by 22% making its execution speed only 3% slower than native (i.e., non-managed) execution.

Metaman

“…When collecting metadata to improve indirect branch handling [21], we examined the effect on memory usage for the Xalan SPEC2006 benchmark [9]. The size of the virtual memory over time, as reported by the ps utility, is shown in Figure 5.…”

“…Such a technique allows the run-time tool to only load the metadata used by that particular run of the program, rather than the entire set of metadata that could be used for a given program. We tested this technique by setting up a simple, prototype metadata server, using UNIX sockets to communicate metadata about call-return pairs, useful for improving execution of returns in an SDT [21]. Table 2 shows the run-time overhead of the metadata server.…”

“…Indirect branches cause performance problems in SDT systems because the system must always check the target of an indirect branch each time the branch is executed. Using high-level compile-time information about the source of indirect branches such as the associated virtual function table, Metaman can provide an SDT with enough information to generate a completely translated indirect branch, and not rely on hashtable-based run lookup mechanisms, thus avoiding the performance penalty [21].…”