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Modern programming languages offer abstractions that simplify software development and allow hardware to reach its full potential. These abstractions range from the well-established OpenMP language extensions to newer C++ features like smart pointers. To properly use these abstractions in an existing codebase, programmers must determine how a given source code region interacts with Program State Elements (PSEs) (i.e., the program's variables and memory locations). We call this process Program State Element Characterization (PSEC). Without tool support for PSEC, a programmer's only option is to manually study the entire codebase. We propose a profile-based approach that automates PSEC and provides abstraction recommendations to programmers. Because a profile-based approach incurs an impractical overhead, we introduce the Compiler and Runtime Memory Observation Tool (CARMOT), a PSEC-specific compiler co-designed with a parallel runtime. CARMOT reduces the overhead of PSEC by two orders of magnitude, making PSEC practical. We show that CARMOT's recommendations achieve the same speedup as hand-tuned OpenMP directives and avoid memory leaks with C++ smart pointers. From this, we argue that PSEC tools, such as CARMOT, can provide support for the rich ecosystem of modern programming language abstractions.
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Hardware Supported Permission Checks on Persistent Objects for Performance and Programmability
Non-Volatile Memory technologies are advancing rapidly and may augment or replace DRAM in future systems. However, a key question is how programmers will use them to construct and manipulate persistent data. One possible approach gives programmers direct access to persistent memory using relocatable persistent pools that hold persistent objects which can be accessed using persistent pointers, called ObjectIDs. Prior work has shown that hardware-supported address translation for ObjectIDs provides significant performance improvement and simplifies programming, however these works did not consider the large overheads incurred to check permissions before accessing persistent objects. In this paper, we identify permission checking in hardware as a critical mechanism that must be included when translating ObjectIDs to addresses in order to simplify programming and fully benefit from hardware translation. To support it, we add a System Persistent Object Table (SPOT) to support translation and permissions checks on ObjectIDs. The SPOT holds all known pools, their physical address, and their permissions information in memory. When a program attempts to access a persistent object, the SPOT is consulted and permissions are verified without trapping to the operating system. We have implemented our new design in a cycle accurate simulator and compared it with software only approaches and prior work. We find that our design offers a compelling 2.9x speedup on average for microbenchmarks that access pools with the RANDOM pattern and 1.4x and 1.8x speedup on TPC-C and vacation, respectively, for the SEPARATE pattern.
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- Award ID(s):
- 1717486
- PAR ID:
- 10077433
- Date Published:
- Journal Name:
- International Symposium on Computer Architecture
- Page Range / eLocation ID:
- 466 to 478
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/ISCA.2018.00046
