http://idning.github.io/gcc_gdb_gprof_gcov_valgrind.html
gcov 函数执行频率
gcov is a test coverage program how often each line of code executes what lines of code are actually executed how much computing time each section of code uses
When using gcov, you must first compile your program with two special GCC options: -fprofile-arcs -ftest-coverage.
For each source file compiled with -fprofile-arcs, an accompanying .gcda file will be placed in the object file directory. usage:
$ gcc -fprofile-arcs -ftest-coverage tmp.c
$ ./a.out
$ gcov tmp.c
90.00% of 10 source lines executed in file tmp.c
Creating tmp.c.gcov.
The file tmp.c.gcov contains output from gcov. Here is a sample:
-: 0:Source:tmp.c
-: 0:Graph:tmp.gcno
-: 0:Data:tmp.gcda
-: 0:Runs:1
-: 0:Programs:1
-: 1:#include <stdio.h>
-: 2:
-: 3:int main (void)
1: 4:{
1: 5: int i, total;
-: 6:
1: 7: total = 0;
-: 8:
11: 9: for (i = 0; i < 10; i++)
10: 10: total += i;
-: 11:
1: 12: if (total != 45)
#####: 13: printf ("Failure\n");
-: 14: else
1: 15: printf ("Success\n");
1: 16: return 0;
-: 17:}
编译时: -fprofile-arcs -ftest-coverage 链接时: -l gcov
The .gcno file is generated when the source file is compiled with the GCC -ftest-coverage option. It contains information to reconstruct the basic block graphs and assign source line numbers to blocks. The .gcda file is generated when a program containing object files built with the GCC -fprofile-arcs option is executed. A separate.gcda file is created for each object file compiled with this option. It contains arc transition counts, and some summary information.
内存泄漏
Valgrind
valgrind --tool=memcheck --leak-check=full -v --log-file=lighttpd --num-callers=8 ./bin/lighttpd -D -f ./conf/lighttpd.conf
Valgrind的主要功能 Valgrind工具包包含多个工具，如Memcheck,Cachegrind,Helgrind, Callgrind，Massif。
Memcheck 工具主要检查下面的程序错误：
• 使用未初始化的内存 (Use of uninitialised memory)
• 使用已经释放了的内存 (Reading/writing memory after it has been free’d)
• 使用超过 malloc分配的内存空间(Reading/writing off the end of malloc’d blocks)
• 对堆栈的非法访问 (Reading/writing inappropriate areas on the stack)
• 申请的空间是否有释放 (Memory leaks – where pointers to malloc’d blocks are lost forever)
• malloc/free/new/delete申请和释放内存的匹配(Mismatched use of malloc/new/new [] vs free/delete/delete [])
• src和dst的重叠(Overlapping src and dst pointers in memcpy() and related functions)
Callgrind收集程序运行时的一些数据，函数调用关系等信息，还可以有选择地进行cache 模拟。
在运行结束时，它会把分析数据写入一个文件。callgrind_annotate可以把这个文件的内容转化成可读的形式。 Cachegrind 它模拟 CPU中的一级缓存I1,D1和L2二级缓存，能够精确地指出程序中 cache的丢失和命中。
如果需要，它还能够为我们提供cache丢失次数，内存引用次数，以及每行代码，每个函数，每个模块，整个程序产生的指令数。这对优化程序有很大的帮助。
Helgrind 它主要用来检查多线程程序中出现的竞争问题。
Helgrind 寻找内存中被多个线程访问，而又没有一贯加锁的区域，这些区域往往是线程之间失去同步的地方，而且会导致难以发掘的错误。Helgrind实现了名为” Eraser” 的竞争检测算法，并做了进一步改进，减少了报告错误的次数。
Massif 堆栈分析器，它能测量程序在堆栈中使用了多少内存，告诉我们堆块，堆管理块和栈的大小。Massif能帮助我们减少内存的使用，在带有虚拟内存的现代系统中，它还能够加速我们程序的运行，减少程序停留在交换区中的几率。
perf
速度快. 2.6内核提供的. ubuntu, centos都默认安装, 不需要root
perf top:
直接看到热点
perf list:
List of pre-defined events (to be used in -e): cpu-cycles OR cycles [Hardware event] instructions [Hardware event] cache-references [Hardware event] cache-misses [Hardware event] 可以统计cache-miss噢. page-faults OR faults [Software event]
有点像strace 对系统调用计数 .
使用:
perf stat -e cycles dd if=/dev/zero of=/dev/null count=100000
attach:
perf stat -e cycles -p 2262 sleep 2
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