用gprof时time都是0咋办？

lovememememe 2007-08-16 10:54:34

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性能分析，函数调用关系清晰，cputime分析明了，非常方便易懂，易于开发中优化code性能

背景使用C++开发了一个Redis数据导入工具从oracle中将所有表数据导入到redis中；不是单纯的数据导入，每条oracle中的原有记录，需要经过业务逻辑处理，并添加索引（redis集合）；工具完成后，性能是个瓶颈；优化效果使用了2个样本数据测试：样本数据a表8763 条记录； b表940279 条记录；优化前，a表耗时11.417s；优化后，a表耗时1.883s；用到的工具 gprof, pstrace,time 使用time工具查看每次执行的耗时，分别包含用户时间和系统时间；使用pstrace打印实时运行，查询进程主要的系统调用，发现耗时点；

项目要点：Darknet原理、天河超算平台使用、MakeFile、安装及运行、卷积神经网络算法YOLO、im2col、GEMM矩阵乘、gprof工具做性能分析、统计优化结果并编写文档；掌握技能：高性能计算与超级计算机 Linux 常用操作...

High Resolution Profiler 是一个库，它使用 Pentium Time Stamp Counter 来测量程序中各种函数使用的时间，并编写一个与现有 gprof 程序兼容的 gmon.out 文件。

1 You Write Software; You have Bugs . . . . . . . . . 1 2 A Systematic Approach to Debugging . . . . . . . 5 2.1 Why Follow a Structured Process? . . . . . . . 5 2.2 Making the Most of Your Opportunities . . . . . . 5 2.3 13 Golden Rules . . . . . . . . . . . . . 7 2.3.1 Understand the Requirements . . . . . . 8 2.3.2 Make it Fail . . . . . . . . . . . . 8 2.3.3 Simplify the Test Case . . . . . . . . . 9 2.3.4 Read the Right Error Message . . . . . . 9 2.3.5 Check the Plug . . . . . . . . . 9 2.3.6 Separate Facts from Interpretation . . . . . 10 2.3.7 Divide and Conquer . . . . . . . . 10 2.3.8 Match the Tool to the Bug . . . . . . . . . 12 2.3.9 One Change at a Time . . . . . . . . . 12 2.3.10 Keep an Audit Trail . . . . . . . . 12 2.3.11 Get a Fresh View . . . . . . . . . . . 13 2.3.12 If You Didn’t Fix it, it Ain’t Fixed . . . . . 13 2.3.13 Cover your Bugfix with a Regression Test . . . . . 13 2.4 Build a Good Toolkit . . . . . . . . . . . . 14 2.4.1 Your Workshop . . . . . . . . . 15 2.4.2 Running Tests Every Day Keeps the Bugs at Bay . . 15 2.5 Know Your Enemy – Meet the Bug Family . . . . . . 17 2.5.1 The Common Bug . . . . . . . . . . 17 2.5.2 Sporadic Bugs . . . . . . . . . . 18 2.5.3 Heisenbugs. . . . . . . . . . 18 2.5.4 Bugs Hiding Behind Bugs . . . . . . . . . 19 2.5.5 Secret Bugs – Debugging and Confidentiality . . . . . 20 2.5.6 Further Reading . . . . . . . . . 21 3 Getting to the Root – Source Code Debuggers . . . . . . 23 3.1 Visualizing Program Behavior . . . . . . . . 23 3.2 Prepare a Simple Predictable Example . . . . . . . 24 3.3 Get the Debugger to Run with Your Program . . . . . . . 24 3.4 Learn to do a Stack Trace on a Program Crash . . . . . . 27 3.5 Learn to Use Breakpoints . . . . . . . . . 28 3.6 Learn to Navigate Through the Program. . . . . . 28 3.7 Learn to Inspect Data: Variables and Expressions . . . . 29 3.8 A Debug Session on a Simple Example . . . . . . 30 4 Fixing Memory Problems . . . . . . . . . . . . 33 4.1 Memory Management in C/C++ – Powerful but Dangerous . . . . 33 4.1.1 Memory Leaks . . . . . . . . . 34 4.1.2 Incorrect Use of Memory Management . . . . 34 4.1.3 Buffer Overruns . . . . . . . . . . . 34 4.1.4 Uninitialized Memory Bugs . . . . . . . . 34 4.2 Memory Debuggers to the Rescue . . . . . . . . 35 4.3 Example 1: Detecting Memory Access Errors . . . . . . . 36 4.3.1 Detecting an Invalid Write Access . . . . . 36 4.3.2 Detecting Uninitialized Memory Reads . . . . 37 4.3.3 Detecting Memory Leaks . . . . . . . 38 4.4 Example 2: Broken Calls to Memory Allocation/Deallocation . . 38 4.5 Combining Memory and Source Code Debuggers . . . . . . 40 4.6 Cutting Down the Noise – Suppressing Errors . . . . . . . 40 4.7 When to Use a Memory Debugger . . . . . . . 41 4.8 Restrictions . . . . . . . . . . . . . . 42 4.8.1 Prepare Test Cases with Good Code Coverage . . . . 42 4.8.2 Provide Additional Computer Resources . . . . . . 42 4.8.3 Multi-Threading May Not be Supported . . . . . . 42 4.8.4 Support for Non-standard Memory Handlers . . . 42 5 Profiling Memory Use . . . . . . . . . . . . 45 5.1 Basic Strategy – The First Steps . . . . . . . . . 45 5.2 Example 1: Allocating Arrays . . . . . . . . 46 5.3 Step 1: Look for Leaks . . . . . . . . . . . 46 5.4 Step 2: Set Your Expectations . . . . . . . . 47 5.5 Step 3: Measure Memory Consumption . . . . . . 47 5.5.1 Use Multiple Inputs . . . . . . . . 48 5.5.2 Stopping the Program at Regular Intervals . . . . . 48 5.5.3 Measuring Memory Consumption with Simple Tools . . 49 5.5.4 Use top . . . . . . . . . . . . 49 5.5.5 Use the Windows Task Manager . . . . . . . 50 5.5.6 Select Relevant Input Values for testmalloc . . . 51 5.5.7 Determine how Memory is Deallocated on Your Machine . 51 5.5.8 Use a Memory Profiler . . . . . . . . . 53 5.6 Step 4: Identifying Greedy Data Structures . . . . . . 54 5.6.1 Instrumenting Data Structures . . . . . . 55 5.7 Putting it Together – The genindex Example. . . . . . 55 5.7.1 Check that There are No Major Leaks . . . . . 56 5.7.2 Estimate the Expected Memory Use . . . . . . . 56 5.7.3 Measure Memory Consumption . . . . . . . 57 5.7.4 Find the Data Structures that Consume Memory . . . 57 6 Solving Performance Problems . . . . . . . . . . 63 6.1 Finding Performance Bugs – A Step-by-Step Approach . . . . . 63 6.1.1 Do an Upfront Analysis . . . . . . . . 64 6.1.2 Use a Simple Method of Measuring Time . . . . . 64 6.1.3 Create a Test Case . . . . . . . . . . 65 6.1.4 Make the Test Case Reproducible . . . . . . 65 6.1.5 Check the Program for Correctness . . . . . . . 66 6.1.6 Make the Test Case Scalable . . . . . . . 66 6.1.7 Isolate the Test Case from Side Effects . . . . 67 6.1.8 Measurement with time can have Errors and Variations . 68 6.1.9 Select a Test Case that Exposes the Runtime Bottleneck . . 68 6.1.10 The Difference Between Algorithm and Implementation . . 70 6.2 Using Profiling Tools . . . . . . . . . . . . 72 6.2.1 Do Not Write Your Own Profiler . . . . . . . 72 6.2.2 How Profilers Work . . . . . . . . 73 6.2.3 Familiarize Yourself with gprof . . . . . . 74 6.2.4 Familiarize Yourself with Quantify . . . . . 79 6.2.5 Familiarize Yourself with Callgrind . . . . . . . 81 6.2.6 Familiarize Yourself with VTune . . . . . . 82 6.3 Analyzing I/O Performance . . . . . . . . . . 84 6.3.1 Do a Sanity Check of Your Measurements . . . . . 85 7 Debugging Parallel Programs . . . . . . . . . 87 7.1 Writing Parallel Programs in C/C++ . . . . . . . . . 87 7.2 Debugging Race Conditions . . . . . . . . . . 88 7.2.1 Using Basic Debugger Capabilities to Find Race Conditions . . . . . . . . . . 89 7.2.2 Using Log Files to Localize Race Conditions . . . . . 91 7.3 Debugging Deadlocks . . . . . . . . . . . . 93 7.3.1 How to Determine What the Current Thread is Executing . 94 7.3.2 Analyzing the Threads of the Program . . . . . 95 7.4 Familiarize Yourself with Threading Analysis Tools . . . . . 96 7.5 Asynchronous Events and Interrupt Handlers . . . . . . . 98 8 Finding Environment and Compiler Problems . . . . . . 101 8.1 Environment Changes – Where Problems Begin . . . . . 101 8.1.1 Environment Variables . . . . . . . . . 101 8.1.2 Local Installation Dependencies . . . . . . . 102 8.1.3 Current Working Directory Dependency . . . . . . 102 8.1.4 Process ID Dependency . . . . . . . . 102 8.2 How else to See what a Program is Doing . . . . . . . 103 8.2.1 Viewing Processes with top . . . . . . . 103 8.2.2 Finding Multiple Processes of an Application with ps . . . 103 8.2.3 Using /proc/ to Access a Process . . . . 104 8.2.4 Use strace to Trace Calls to the OS . . . . . 104 8.3 Compilers and Debuggers have Bugs too . . . . . . . . 106 8.3.1 Compiler Bugs . . . . . . . . . 106 8.3.2 Debugger and Compiler Compatibility Problems . . 107 9 Dealing with Linking Problems . . . . . . . . . . 109 9.1 How a Linker Works . . . . . . . . . . 109 9.2 Building and Linking Objects . . . . . . . . 110 9.3 Resolving Undefined Symbols . . . . . . . . 111 9.3.1 Missing Linker Arguments . . . . . . . . 111 9.3.2 Searching for Missing Symbols . . . . . . . . 112 9.3.3 Linking Order Issues . . . . . . . . . . 113 9.3.4 C++ Symbols and Name Mangling . . . . . 114 9.3.5 Demangling of Symbols . . . . . . . . 115 9.3.6 Linking C and C++ Code . . . . . . . 115 9.4 Symbols with Multiple Definitions . . . . . . . 116 9.5 Symbol Clashes . . . . . . . . . . . 117 9.6 Identifying Compiler and Linker Version Mismatches . . . 118 9.6.1 Mismatching System Libraries . . . . . . . . 119 9.6.2 Mismatching Object Files . . . . . . . . . 119 9.6.3 Runtime Crashes . . . . . . . . . . . 120 9.6.4 Determining the Compiler Version . . . . . 120 9.7 Solving Dynamic Linking Issues . . . . . . . . . 122 9.7.1 Linking or Loading DLLs . . . . . . . . . 122 9.7.2 DLL Not Found . . . . . . . . . 124 9.7.3 Analyzing Loader Issues . . . . . . . 125 9.7.4 Setting Breakpoints in DLLs . . . . . . . 126 9.7.5 Provide Error Messages for DLL Issues . . . . 127 10 Advanced Debugging . . . . . . . . . . . . . 129 10.1 Setting Breakpoints in C++ Functions, Methods, and Operators . 129 10.2 Setting Breakpoints in Templatized Functions and C++ Classes . 131 10.3 Stepping in C++ Methods . . . . . . . . . 133 10.3.1 Stepping into Implicit Functions . . . . . . . 134 10.3.2 Skipping Implicit Functions with the Step-out Command . 135 10.3.3 Skipping Implicit Functions with a Temporary Breakpoint 136 10.3.4 Returning from Implicit Function Calls . . . . 136 10.4 Conditional Breakpoints and Breakpoint Commands . . . . 137 10.5 Debugging Static Constructor/Destructor Problems . . . . . 140 10.5.1 Bugs Due to Order-Dependence of Static Initializers . . 140 10.5.2 Recognizing the Stack Trace of Static Initializers . . 141 10.5.3 Attaching the Debugger Before Static Initialization . . . 142 10.6 Using Watchpoints . . . . . . . . . . . 143 10.7 Catching Signals . . . . . . . . . . . . . 144 10.8 Catching Exceptions . . . . . . . . . . 147 10.9 Reading Stack Traces . . . . . . . . . . . . 148 10.9.1 Stack Trace of Source Code Compiled with Debug Information . . . . . . . . 148 10.9.2 Stack Trace of Source Code Compiled Without Debug Information . . . . . . . . 149 10.9.3 Frames Without Any Debug Information . . . . . . 149 10.9.4 Real-Life Stack Traces . . . . . . . . . 150 10.9.5 Mangled Function Names . . . . . . . . . 151 10.9.6 Broken Stack Traces . . . . . . . . 151 10.9.7 Core Dumps . . . . . . . . . . . . 152 10.10 Manipulating a Running Program . . . . . . . . 153 10.10.1 Changing a Variable . . . . . . . . 156 10.10.2 Calling Functions . . . . . . . . . . 156 10.10.3 Changing the Return Value of a Function . . . . . . 157 10.10.4 Aborting Function Calls . . . . . . . . 157 10.10.5 Skipping or Repeating Individual Statements . . . . . 158 10.10.6 Printing and Modifying Memory Content . . . . . 159 10.11Debugging Without Debug Information . . . . . . 161 10.11.1 Reading Function Arguments From the Stack . . . . . 163 10.11.2 Reading Local/Global Variables, User-Defined Data Types 165 10.11.3 Finding the Approximate Statement in the Source Code . . 165 10.11.4 Stepping Through Assembly Code . . . . . 166 11 Writing Debuggable Code . . . . . . . . . . . . 169 11.1 Why Comments Count . . . . . . . . . . . 169 11.1.1 Comments on Function Signatures . . . . . 170 11.1.2 Comments on Workarounds . . . . . . . . 171 11.1.3 Comments in Case of Doubt . . . . . . . 171 11.2 Adopting a Consistent Programming Style . . . . . . 171 11.2.1 Choose Names Carefully . . . . . . . 171 11.2.2 Avoid Insanely Clever Constructs . . . . . . 172 11.2.3 Spread Out Your Code . . . . . . . . . 172 11.2.4 Use Temporary Variables for Complex Expressions . . . 172 11.3 Avoiding Preprocessor Macros . . . . . . . . . . 173 11.3.1 Use Constants or Enums Instead of Macros . . . . 173 11.3.2 Use Functions Instead of Preprocessor Macros . . . . 175 11.3.3 Debug the Preprocessor Output . . . . . . . . 176 11.3.4 Consider Using More Powerful Preprocessors . . . . 177 11.4 Providing Additional Debugging Functions . . . . . . 179 11.4.1 Displaying User-Defined Data Types . . . . . . 179 11.4.2 Self-Checking Code . . . . . . . . 180 11.4.3 Debug Helpers for Operators . . . . . . . 181 11.5 Prepare for Post-Processing . . . . . . . . . . 181 11.5.1 Generate Log Files . . . . . . . . . 181 12 How Static Checking Can Help . . . . . . . . . . 183 12.1 Using Compilers as Debugging Tools . . . . . . . . 183 12.1.1 Do not Assume Warnings to be Harmless . . . . . 184 12.1.2 Use Multiple Compilers to Check the Code . . . . 186 12.2 Using lint . . . . . . . . . . . . . . 186 12.3 Using Static Analysis Tools . . . . . . . . . . 187 12.3.1 Familiarize Yourself with a Static Checker . . . . 187 12.3.2 Reduce Static Checker Errors to (Almost) Zero . . . 189 12.3.3 Rerun All Test Cases After a Code Cleanup . . . 190 12.4 Beyond Static Analysis . . . . . . . . . . . 190 13 Summary . . . . . . . . . . . . . . 191 A Debugger Commands . . . . . . . . . . . . . 193 B Access to Tools . . . . . . . . . . . . . 195 B.1 IDEs, Compilers, Build Tools . . . . . . . . 195 B.1.1 Microsoft Visual Studio . . . . . . . . 195 B.1.2 Eclipse . . . . . . . . . . . . . 196 B.1.3 GCC . . . . . . . . . . . . 196 B.1.4 GNU Make . . . . . . . . . . . . 196 B.2 Debuggers . . . . . . . . . . . . 196 B.2.1 dbx . . . . . . . . . . . . . 196 B.2.2 DDD . . . . . . . . . . . . 197 B.2.3 GDB . . . . . . . . . . . . 197 B.2.4 ARM RealView . . . . . . . . . 197 B.2.5 TotalView Debugger . . . . . . . . 197 B.2.6 Lauterbach TRACE32 . . . . . . . . . 197 B.3 Environments . . . . . . . . . . . . . 198 B.3.1 Cygwin . . . . . . . . . . . . . 198 B.3.2 VMware . . . . . . . . . . . . 198 B.4 Memory Debuggers . . . . . . . . . . . 198 B.4.1 Purify . . . . . . . . . . . 198 B.4.2 Valgrind . . . . . . . . . . . . 199 B.4.3 KCachegrind . . . . . . . . . . . 199 B.4.4 Insure++ . . . . . . . . . . . . 199 B.4.5 BoundsChecker . . . . . . . . . 200 B.5 Profilers . . . . . . . . . . . . . . 200 B.5.1 gprof . . . . . . . . . . . . 200 B.5.2 Quantify . . . . . . . . . . . . 200 B.5.3 Intel VTune . . . . . . . . . . . . 200 B.5.4 AQtime . . . . . . . . . . . . . 201 B.5.5 mpatrol . . . . . . . . . . . . . 201 B.6 Static Checkers . . . . . . . . . . . 201 B.6.1 Coverity . . . . . . . . . . . . 201 B.6.2 Lint . . . . . . . . . . . . . 201 B.6.3 Splint . . . . . . . . . . . 202 B.6.4 /analyze option in Visual Studio Enterprise Versions . . 202 B.6.5 Klocwork . . . . . . . . . . . 202 B.6.6 Fortify . . . . . . . . . . . . . 202 B.6.7 PC-lint/FlexeLint . . . . . . . . . . 203 B.6.8 QA C++ . . . . . . . . . . . . 203 B.6.9 Codecheck . . . . . . . . . . 203 B.6.10 Axivion Bauhaus Suite . . . . . . . . . 203 B.6.11 C++ SoftBench CodeAdvisor . . . . . . 203 B.6.12 Parasoft C++test . . . . . . . . . . . 204 B.6.13 LDRA tool suite . . . . . . . . . . . 204 B.6.14 Understand C++ . . . . . . . . . . . 204 B.7 Tools for Parallel Programming . . . . . . . . . . 204 B.7.1 Posix Threads . . . . . . . . . . 204 B.7.2 OpenMP . . . . . . . . . . . . 204 B.7.3 Intel TBB . . . . . . . . . . . 205 B.7.4 MPI . . . . . . . . . . . . . 205 B.7.5 MapReduce . . . . . . . . . . . . 205 B.7.6 Intel Threading Analysis Tools . . . . . . . . 205 B.8 Miscellaneous Tools . . . . . . . . . . 206 B.8.1 GNU Binutils . . . . . . . . . . . 206 B.8.2 m4 . . . . . . . . . . . . . . 206 B.8.3 ps . . . . . . . . . . . . . . 206 B.8.4 strace / truss . . . . . . . . . . 207 B.8.5 top. . . . . . . . . . . . . 207 B.8.6 VNC . . . . . . . . . . . . 207 B.8.7 WebEx . . . . . . . . . . . . . 207 C Source Code . . . . . . . . . . . . . . . 209 C.1 testmalloc.c . . . . . . . . . . . . . . 209 C.2 genindex.c . . . . . . . . . . . . 210 C.3 isort.c . . . . . . . . . . . . . 214 C.4 filebug.c . . . . . . . . . . . . . . 216 References . . . . . . . . . . . . . . 217 Index . . . . . . . . . . . . . . . . 219

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