http://www.linuxidc.com/Linux/2012-06/63754.htm
still reachable
多数情况不是问题，比如程序是一个服务，一直运行一个while循环，而new出来的对象如果只能在析构delete，那么对象就永远不会被释放，valgrind就会报这样的问题
一 Valgrind工具集简绍
Valgrind包含下列工具：
1、memcheck：检查程序中的内存问题，如泄漏、越界、非法指针等。
2、callgrind：检测程序代码的运行时间和调用过程，以及分析程序性能。
3、cachegrind：分析CPU的cache命中率、丢失率，用于进行代码优化。
4、helgrind：用于检查多线程程序的竞态条件。
5、massif：堆栈分析器，指示程序中使用了多少堆内存等信息。
6、lackey：
7、nulgrind：
1.Memcheck
最常用的工具，用来检测程序中出现的内存问题，所有对内存的读写都会被检测到，一切对malloc、free、new、delete的调用都会被捕获。所以，它能检测以下问题：
1、对未初始化内存的使用；
2、读/写释放后的内存块；
3、读/写超出malloc分配的内存块；
4、读/写不适当的栈中内存块；
5、内存泄漏，指向一块内存的指针永远丢失；
6、不正确的malloc/free或new/delete匹配；
7、memcpy()相关函数中的dst和src指针重叠。
存泄露检测
$ valgrind --leak-check=full --show-reachable=yes --trace-children=yes ./iquery -f ../conf/se.conf_forum -t ~/eragon/forum_thread_data/f.log -NT -cache 0
其中--leak-check=full 指的是完全检查内存泄漏，--show-reachable=yes是显示内存泄漏的地点，--trace-children=yes是跟入子进程。当程序正常退出的时候valgrind自然会输出内存泄漏的信息。
==4591==
==4591== Thread 1:
==4591== Conditional jump or move depends on uninitialised value(s)
==4591== at 0x805687B: main (TestQuery.cpp:478)
==4591==
==4591== Conditional jump or move depends on uninitialised value(s)
==4591== at 0x8056894: main (TestQuery.cpp:478)
==4591==
==4591== Conditional jump or move depends on uninitialised value(s)
==4591== at 0x80568AD: main (TestQuery.cpp:478)
==4591== Warning: set address range perms: large range 215212032 (noaccess)
==4591== Warning: set address range perms: large range 125145088 (noaccess)
==4591==
==4591== ERROR SUMMARY: 6 errors from 4 contexts (suppressed: 18 from 1)
==4591== malloc/free: in use at exit: 496 bytes in 2 blocks.
==4591== malloc/free: 928,605 allocs, 928,603 frees, 2,514,165,074 bytes allocated.
==4591== For counts of detected errors, rerun with: -v
==4591== searching for pointers to 2 not-freed blocks.
==4591== checked 10,260,564 bytes.
==4591==
==4591==
==4591== 144 bytes in 1 blocks are possibly lost in loss record 1 of 2
==4591== at 0x4005906: calloc (vg_replace_malloc.c:279)
==4591== by 0xB3671A: _dl_allocate_tls (in /lib/ld-2.3.4.so)
==4591== by 0xD9491E: pthread_create@@GLIBC_2.1 (in /lib/tls/libpthread-2.3.4.so)
==4591== by 0x8200C66: public_unit::CThread::start(void*) (Thread.cpp:25)
==4591== by 0x80567C3: main (TestQuery.cpp:473)
==4591==
==4591==
==4591== 352 bytes in 1 blocks are still reachable in loss record 2 of 2
==4591== at 0x40044F6: malloc (vg_replace_malloc.c:149)
==4591== by 0xB9905E: __fopen_internal (in /lib/tls/libc-2.3.4.so)
==4591== by 0xB9911C: fopen@@GLIBC_2.1 (in /lib/tls/libc-2.3.4.so)
==4591== by 0x805940C: CSearchThread::run(void*) (TestQuery.cpp:363)
==4591== by 0x8200D09: public_unit::CThread::thread_func(void*) (Thread.cpp:44)
==4591== by 0xD94370: start_thread (in /lib/tls/libpthread-2.3.4.so)
==4591== by 0xC0DFFD: clone (in /lib/tls/libc-2.3.4.so)
==4591==
==4591== LEAK SUMMARY:
==4591== definitely lost: 0 bytes in 0 blocks.
==4591== possibly lost: 144 bytes in 1 blocks.
==4591== still reachable: 352 bytes in 1 blocks.
==4591== suppressed: 0 bytes in 0 blocks.
关键字在：ERROR SUMMARY, LEAK SUMMARY
"definitely lost" means your program is leaking memory -- fix it!
"possibly lost" means your program is probably leaking memory, unless you're doing funny things with pointers.
"still reachable" means your program is probably ok -- it didn't freesome memory it could have. This is quite common and often reasonable.Don't use --show-reachable=yes if you don't want to see these reports.
"suppressed" means that a leak error has been suppressed. There aresome suppressions in the default suppression files. You can ignoresuppressed errors
另外一种方式，激活加载调试器
gcc -Wall -g -pg -o get_XMLDOC get_XMLDOC.c
$ valgrind --db-attach=yes --leak-check=full ./get_XMLDOC ~/eragon/data/offer_gb.xml 1.xml 10
==8956== Memcheck, a memory error detector.
==8956== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.
==8956== Using LibVEX rev 1606, a library for dynamic binary translation.
==8956== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.
==8956== Using valgrind-3.2.0, a dynamic binary instrumentation framework.
==8956== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.
==8956== For more details, rerun with: -v
==8956==
==8956==
==8956== ---- Attach to debugger ? --- [Return/N/n/Y/y/C/c] ----
==8956==
==8956== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 12 from 1)
==8956== malloc/free: in use at exit: 1,953 bytes in 2 blocks.
==8956== malloc/free: 4 allocs, 2 frees, 2,657 bytes allocated.
==8956== For counts of detected errors, rerun with: -v
==8956== searching for pointers to 2 not-freed blocks.
==8956== checked 52,840 bytes.
==8956==
==8956== 1 bytes in 1 blocks are definitely lost in loss record 1 of 2
==8956== at 0x40044F6: malloc (vg_replace_malloc.c:149)
==8956== by 0x80488C0: main (get_XMLDOC.c:38)
==8956==
==8956== LEAK SUMMARY:
==8956== definitely lost: 1 bytes in 1 blocks.
==8956== possibly lost: 0 bytes in 0 blocks.
==8956== still reachable: 1,952 bytes in 1 blocks.
==8956== suppressed: 0 bytes in 0 blocks.
==8956== Reachable blocks (those to which a pointer was found) are not shown.
==8956== To see them, rerun with: --show-reachable=yes
Profiling timer expired
2.4. 检查性能瓶颈
$valgrind --tool=callgrind ./iquery -f ../conf/se.conf_forum -s "forum_thread?q=mp4"
…
==4607==
==4607== Events : Ir
==4607== Collected : 251772397
==4607==
==4607== I refs: 251,772,397
4607为进程号。
$ ll
-rw------- 1 search search 712159 7月 9 22:31 callgrind.out.4607
$ callgrind_annotate --auto=yes callgrind.out.4607
WARNING: header line 2 malformed, ignoring
line: 'creator: callgrind-3.2.0'
--------------------------------------------------------------------------------
I1 cache:
D1 cache:
L2 cache:
Timerange: Basic block 0 - 46942078
Trigger: Program termination
Profiled target: ./iquery -f ../conf/se.conf_forum -s forum_thread?q=mp4 (PID 4607, part 1)
Events recorded: Ir
Events shown: Ir
Event sort order: Ir
Thresholds: 99
Include dirs:
User annotated:
Auto-annotation: on
--------------------------------------------------------------------------------
Ir
--------------------------------------------------------------------------------
251,772,397 PROGRAM TOTALS
--------------------------------------------------------------------------------
Ir file:function
--------------------------------------------------------------------------------
54,769,656 ???:__mcount_internal [/lib/tls/libc-2.3.4.so]
26,418,450 GBKNormalString.cpp:dictionary::CGBKNormalString::initNormalChars() [/home/search/eragon_yb/bin/iquery]
22,820,690 ???:mcount [/lib/tls/libc-2.3.4.so]
11,559,615 GBKNormalString.cpp:dictionary::CGBKNormalString::initCharKinds() [/home/search/eragon_yb/bin/iquery]
更多说明参考：
http://www-128.ibm.com/developerworks/cn/linux/l-pow-debug/
2.5. cache测试
参考：http://www.wangcong.org/articles/valgrind.html
[search@alitest146 /home/search/eragon_yb/bin]
$ valgrind --tool=cachegrind ./iquery -f ../conf/se.conf_forum -s "forum_thread?q=mp3"
==8742==
==8742== I refs: 267,968,791
==8742== I1 misses: 98,845
==8742== L2i misses: 13,382
==8742== I1 miss rate: 0.03%
==8742== L2i miss rate: 0.00%
==8742==
==8742== D refs: 182,288,669 (120,222,370 rd + 62,066,299 wr)
==8742== D1 misses: 962,816 ( 537,889 rd + 424,927 wr)
==8742== L2d misses: 707,813 ( 340,925 rd + 366,888 wr)
==8742== D1 miss rate: 0.5% ( 0.4% + 0.6% )
==8742== L2d miss rate: 0.3% ( 0.2% + 0.5% )
==8742==
==8742== L2 refs: 1,061,661 ( 636,734 rd + 424,927 wr)
==8742== L2 misses: 721,195 ( 354,307 rd + 366,888 wr)
==8742== L2 miss rate: 0.1% ( 0.0% + 0.5% )
上面的是指令缓存，I1和L2i缓存，的访问信息，包括总的访问次数，丢失次数，丢失率。
中间的是数据缓存，D1和L2d缓存，的访问的相关信息，下面的L2缓存单独的信息。Cachegrind也生成一个文件，名为cachegrind.out.pid，可以通过cg_annotate来读取。输出是一个更详细的列表。Massif的使用和cachegrind类似，不过它也会生成一个名为massif.pid.ps的PostScript文件，里面只有一幅描述堆栈使用状况的彩图。
[search@alitest146 /home/search/Isearchv3_Script_yb/tools]
$ ll cachegrind.out*
-rw------- 1 search search 7283 Jul 11 11:21 cachegrind.out. 8633
$ cg_annotate --8633 --auto=yes ~/isearch_yb/src/test/core/TestQuery.cpp
--------------------------------------------------------------------------------
I1 cache: 16384 B, 32 B, 8-way associative
D1 cache: 16384 B, 64 B, 8-way associative
L2 cache: 2097152 B, 64 B, 8-way associative
Command: ./iquery -f ../conf/se.conf_forum -s forum_thread?q=mp3
Data file: cachegrind.out.8633
Events recorded: Ir I1mr I2mr Dr D1mr D2mr Dw D1mw D2mw
Events shown: Ir I1mr I2mr Dr D1mr D2mr Dw D1mw D2mw
Event sort order: Ir I1mr I2mr Dr D1mr D2mr Dw D1mw D2mw
Thresholds: 99 0 0 0 0 0 0 0 0
Include dirs:
User annotated: /home/search/isearch_yb/src/test/core/TestQuery.cpp
Auto-annotation: on
--------------------------------------------------------------------------------
Ir I1mr I2mr Dr D1mr D2mr Dw D1mw D2mw
--------------------------------------------------------------------------------
267,968,791 98,845 13,395 120,222,370 537,889 340,938 62,066,299 424,927 366,883 PROGRAM TOTALS
--------------------------------------------------------------------------------
Ir I1mr I2mr Dr D1mr D2mr Dw D1mw D2mw file:function
--------------------------------------------------------------------------------
56,779,152 28 6 14,194,788 82 3 14,194,788 34 13 ???:__mcount_internal
26,418,450 108 54 12,868,530 22,710 3,028 1,943,010 79,943 30,480 GBKNormalString.cpp:dictionary::CGBKNormalString::initNormalChars()
……
-- User-annotated source: get_XMLDOC.c
--------------------------------------------------------------------------------
Ir I1mr I2mr Dr D1mr D2mr Dw D1mw D2mw
. . . . . . . . . #include "stdio.h"
. . . . . . . . . #define LINE_MAX_LEN 10240
. . . . . . . . . //get part of xml
. . . . . . . . . main(int argc,char *argv[])
10 1 1 0 0 0 1 0 0 {
. . . . . . . . . FILE *fp;
1 0 0 0 0 0 1 0 0 FILE *fpDst =NULL;
. . . . . . . . .
8 1 0 0 0 0 4 1 1 char content[LINE_MAX_LEN+1]={0};
. . . . . . . . . int inumOfdocs;
1 0 0 0 0 0 1 0 0 int currentdocs=0;
1 1 1 0 0 0 1 0 0 int isDocBegin = 0;
1 0 0 0 0 0 1 0 0 int isDocEnd = 0;
. . . . . . . . .
2 0 0 1 0 0 0 0 0 if (argc < 4)
. . . . . . . . . {
. . . . . . . . . printf("usage: get_XMLDOC srcxml dstxml numOfdocs\\n");
. . . . . . . . . exit(1);
. . . . . . . . . }
. . . . . . . . .
7 2 1 2 0 0 3 0 0 inumOfdocs = atoi(argv[3]);
2 0 0 1 0 0 0 0 0 if (inumOfdocs <=0 )