SAVI objects: sharing and virtuality incorporated

Abstract

Direct sharing and storing of memory objects allows high-performance and low-overhead collaboration between parallel processes or application workflows with loosely coupled programs. However, sharing of objects is hindered by the inability to use subtype polymorphism which is common in object-oriented programming languages. That is because implementations of subtype polymorphism in modern compilers rely on using virtual tables stored at process-specific locations, which makes objects unusable in processes other than the creating process.In this paper, we present SAVI Objects, objects with Sharing and Virtuality Incorporated. SAVI Objects support subtype polymorphism but can still be shared across processes and stored in persistent data structures. We propose two different techniques to implement SAVI Objects and evaluate the tradeoffs between them. The first technique is virtual table duplication which adheres to the virtual-table-based implementation of subtype polymorphism, but duplicates virtual tables for shared objects to fixed memory addresses associated with each shared memory region. The second technique is hashing-based dynamic dispatch which re-implements subtype polymorphism using hashing-based look-ups to a global virtual table.Our results show that SAVI Objects enable direct sharing and storing of memory objects that use subtype polymorphism by adding modest overhead costs to object construction and dynamic dispatch time. SAVI Objects thus enable faster inter-process communication, improving the overall performance of production applications that share polymorphic objects.

Puma

“…Memristors have also been proposed for building byteaddressable non-volatile memories. There have been various works centered around system support for non-volatile memory, including file systems [30], memory allocators [11,83], programming models [16,27,106], durable data structures [31,55,113], representation of pointers [18,28,34,35], and architecture support [60,80,82,99].…”

IVT: an efficient method for sharing subtype polymorphic objects

“…For the same reason, libraries supporting shared memory, such as Boost, explicitly forbid sharing polymorphic objects [Boost C++ Libraries 2018c]. Hajj et al [Hajj et al 2017] proposed two techniques to solve this issue, namely virtual table duplication and hashing-based dynamic dispatch. The first technique duplicates virtual tables in a fixed-address region of each process involved in sharing.…”

“…The duplicated virtual tables make the native pointers to virtual tables reusable across processes, as shown in Figure 2(a). Following Hajj et al [Hajj et al 2017], we will refer to this technique as DVT (Duplicate Virtual Table). The second technique totally gets rid of virtual table pointers, and realizes dynamic dispatch by looking up in a global virtual table using a hash number stored in each object, as shown in Figure 2(b).…”

“…The second technique totally gets rid of virtual table pointers, and realizes dynamic dispatch by looking up in a global virtual table using a hash number stored in each object, as shown in Figure 2(b). Following Hajj et al [Hajj et al 2017], we will refer to this technique as GVT (Global Virtual Table).…”

“…Hajj et al [Hajj et al 2017] provide two techniques to solve this problem. But they introduce performance degradation to object construction and dynamic dispatch, which makes them less suitable for scenarios where objects are constructed and accessed constantly.…”