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Date: Tue, 05 Nov 1996 20:37:12 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Tue, 14 May 1996 16:52:45 GMTContent-length: 4077<HTML><HEAD><TITLE> QPT </TITLE><!-- Changed by: James Larus, 14-May-1996 --></HEAD><BODY><H1> QPT: <BR> A Quick Program Profiling and Tracing System </h1><P>QPT is an exact and efficient program profiler and tracing system. Itrewrites a program's executable file (a.out) by inserting code torecord the execution frequency or sequence of every basic block(straight-line sequence of instructions) or control-flow edge. Fromthis information, another program QPT_STATS can calculate theexecution cost of procedures in the program. Unlike the Unix toolsPROF and GPROF, QPT records exact execution frequency, not astatistical sample. When tracing a program, QPT produces a traceregeneration program that reads the highly compressed trace file andregenerates a full program trace.<P>When profiling, QPT operates in two modes. In "slow" mode, it placesa counter in each basic block in a program--in the same manner as theMIPS tool PIXIE. In "quick" mode, QPT places counters on aninfrequently-executed subset of the edges in the program'scontrol-flow graph. This placement can reduce the cost of profilingby 3--4 times. Since there is no such thing as a free lunch, quickprofiling requires more program analysis and consequently slows QPTand QPT_STATS. The additional cost to instrument a program and reportresults, however, is small and is quickly gained back when profilinglong-running programs.<P>Like other systems such as pixie, QPT can rewrite an executable file torecord the sequence of instruction and data references. However, QPT usesabstract execution to reduces the overhead of tracing to 2--6 times aprogram's untraced execution cost. QPT also records a number of semanticsevents--such as loop entry and iteration, function entry and exit, andmemory allocation and deallocation--that other systems do not identify.<P>The original version of this program, QPT, is obsolete and has not beenmaintained for several years. At that time, it ran under DEC's Ultrix on aDECStation (MIPS processor) and Sun's SunOS 4.1.2 on a SPARCstation.<P>QPT2, the new version of QPT, is build on<!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><A HREF="http://www.cs.wisc.edu/~larus/eel.html">EEL,</A>a library for editing executable files. EEL currently runs on SPARC-basedmachines (SunOS and Solaris), though other ports in progress. Themachine-specific code in EEL and QPT2 is collected in a few files. Portingto a new machine requires a couple months of effort.<h2> Documentation </h2><UL><LI>The algorithms in QPT are described in:Thomas Ball and James R. Larus, "Optimally Profiling and TracingPrograms," <EM>ACM Transactions on Programming Languages and Systems(TOPLAS)</EM>, vol. 16, no. 4, July 1994, pp. 1319-1360.<LI>Abstract execution is described in:James R. Larus, "Abstract Execution: A Technique for EfficientlyTracing Programs", Software Practices & Experience, v20, n12,December 1990, pp 1241-1258.<LI>QPT is described in:James R. Larus, "Efficient Program Tracing," IEEE Computer, 26, 5,May 1993, pp 52-61.</UL><h2> Applications </h2><P>David Wood has develop a cache profiler called cprof that uses tracesfrom QPT to report the cache misses caused by statements in a program.CPROF is available as part of <!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><a href="http://www.cs.wisc.edu/~larus/warts.html">WARTS</a>.<h2> Obtaining QPT </h2><P>QPT is available as part of <!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><a href="http://www.cs.wisc.edu/~larus/warts.html">WARTS</a>.<P>QPT and QPT2 are distributed with the full source and a small amount ofdocumentation. QPT and QPT2 are copyrighted by me and is distributed underthe terms of the WARTS license. A copy of the license is available onftp.cs.wisc.edu in <!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><A href="ftp://ftp.cs.wisc.edu/pub/warts/license.ps">~ftp/pub/warts/license.ps,</A> or can be obtained by contacting me at theaddress below.<P><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><a href="http://www.cs.wisc.edu/~larus/larus.html">James Larus</a><br>Computer Sciences Department <br>1210 West Dayton Street <br>University of Wisconsin <br>Madison, WI 53706 <br><P>larus@cs.wisc.edu <br>(608) 262-9519<HR>Last modified: May 14 1996 by James Larus<ADDRESS> <!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><A HREF="http://www.cs.wisc.edu/~larus/larus.html">larus@cs.wisc.edu</A></ADDRESS></body></html>⌨️ 快捷键说明
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