iHarmonizer: improving the disk efficiency of I/O-intensive multithreaded codes

Conference · Fri Jan 01 04:00:00 EST 2010

OSTI ID:1009542

Davis, Marion Kei ^[1]; Wang, Yizhe ^[2]; Jiang, Song ^[2]

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1. Los Alamos National Laboratory
2. WAYNE STATE UNIV.

Challenged by serious power and thermal constraints, and limited by available instruction-level parallelism, processor designs have evolved to multi-core architectures. These architectures, many augmented with native simultaneous multithreading, are driving software developers to use multithreaded programs to exploit thread-level parallelism. While multithreading is well-known to introduce concerns of data dependency and CPU load balance, less known is that the uncertainty of relative progress of thread execution can cause patterns of I/O requests, issued by different threads, to be effectively random and so significantly degrade hard-disk efficiency. This effect can severely offset the performance gains from parallel execution, especially for I/O-intensive programs. Retaining the benefits of multithreading while not reducing I/O efficiency is an urgent and challenging problem. We propose a user-level scheme, iHarmonizer, to streamline the servicing of I/O requests from multiple threads in OpenMP programs. Specifically, we use the compiler to insert code into OpenMP programs so that data usage can be transmitted at run time to a supporting run-time library; this library in turn prefetches data in a disk-friendly way and coordinates threads execution according to the availability of their requested data. Transparently to the programmer, iHarmonizer makes a multithreaded program I/O efficient while maintaining the benefits of parallelism. Our experiments show that iHarmonizer can significantly speed up the execution of a representative set of I/O-intensive scientific benchmarks.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: DOE
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1009542
• Report Number(s): LA-UR-10-02602; LA-UR-10-2602
• Country of Publication: United States
• Language: English

Related Subjects

97 MATHEMATICS AND COMPUTING
AVAILABILITY
BENCHMARKS
COMPUTER ARCHITECTURE
COMPUTER CODES
EFFICIENCY
PERFORMANCE
PROGRAMMING
VELOCITY