14: Asynchronous I/O in .NET framework

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14: Asynchronous I/O
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15: Securing Windows Objects
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Appendix C Performance Results
The example programs have shown a variety of alternative techniques for carrying out the same tasks, such as file copying and ASCII to Unicode file conversion, and it is natural to speculate about the performance advantages of these techniques Application design requires knowledge of, rather than speculation about, the performance impacts of alternative implementations and the potential performance advantages of various Windows versions, hardware configurations, and Windows features, such as threads and asynchronous I/O The timep program, Program 6-2, measures the real (elapsed) time, user time, and system (kernel) time required to execute a program and provides a convenient way to measure performance and determine the effects of alternative programming techniques and designs
Test Configurations
Testing was performed with a representative variety of applications, based on examples in the book and a range of host systems
Applications
The tables in this appendix show the times measured with timep for the test programs running on several different systems The five functionality areas are as follows 1 File copying Several different techniques, such as using the C library and the Windows CopyFile function, are measured to determine the performance impact File copying stresses file I/O without any data processing 2 ASCII to Unicode conversion This shows the effect of memory mapping, larger buffers, the Windows sequential scan flags, and asynchronous I/O Conversion stresses file I/O with a small amount of data processing as the data is moved, and converted, from one buffer to another 3 Pattern searching This uses the grep program in its multiprocess and multithreaded forms Simple sequential processing is also tested and turns out to be competitive with the two parallel search methods on a single processor Pattern searching increases the amount of data processing required and minimizes the output 4 File sorting This shows the effect of memory mapping, in-memory techniques, and multithreading Sorting, at least for large files, emphasizes CPU processing speed over file I/O 5 Multithreaded producer/consumer system This shows the effects of different synchronization techniques for implementing a multithreaded queuing system in order to evaluate the trade-offs discussed in s 810 among CRITICAL_SECTIONs, mutexes, SignalObjectAndWait, and the signal and broadcast condition variable models All application programs were built with Microsoft Visual C++ 70 and 60 as release versions rather than debug versions Running in debug mode can add significant performance overhead Nearly 80 percent overhead was observed in one CPU-intensive test, and the debug executable images can be two or three times larger than the release versions
Host Systems
Performance was measured on four current (as of 2004) systems with a wide variety of CPU, memory,
and OS configurations All use the NTFS file system Data from some older systems is also provided in several cases 1 A 1GHz Pentium laptop running Windows 2000 Professional 2 A 2GHz Intel Celeron laptop running Windows XP 3 A Windows 2000 PC with a Pentium processor 4 A four-processor Windows 2000 Server system, with NT 50 It uses four 18GHz Intel Xeon processors This system shows the effects of a high-performance CPU and multiple processors The file processing examples also show results on an older NT 500 MHz Pentium III PC to contrast FAT and NTFS performance, although FAT is no longer as common as it once was All file systems were less than 50 percent full and were not significantly fragmented In addition, the systems were all idle, except for running the test programs The CPU-intensive applicationsthe sort programs in particulargave a good indication of relative processing speeds