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  Valgrind 是一款 Linux下(支持 x86、x86_64和ppc32)程序的内存调试工具,它可以对编译后的二进制程序进行内存使用监测(C语言中的malloc和free,以及C++中的new和delete),找出内存泄漏问题。

  Valgrind 中包含的 Memcheck 工具可以检查以下的程序错误:

  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)
  重复free

  1、编译安装 Valgrind:
wget http://valgrind.org/downloads/valgrind-3.4.1.tar.bz2
tar xvf valgrind-3.4.1.tar.bz2
cd valgrind-3.4.1/
./configure --prefix=/usr/local/webserver/valgrind
make
make install


  2、使用示例:对“ls”程序进程检查,返回结果中的“definitely lost: 0 bytes in 0 blocks.”表示没有内存泄漏。
[root@xoyo42 /]# /usr/local/webserver/valgrind/bin/valgrind --tool=memcheck --leak-check=full ls /
==1157== Memcheck, a memory error detector.
==1157== Copyright (C) 2002-2008, and GNU GPL'd, by Julian Seward et al.
==1157== Using LibVEX rev 1884, a library for dynamic binary translation.
==1157== Copyright (C) 2004-2008, and GNU GPL'd, by OpenWorks LLP.
==1157== Using valgrind-3.4.1, a dynamic binary instrumentation framework.
==1157== Copyright (C) 2000-2008, and GNU GPL'd, by Julian Seward et al.
==1157== For more details, rerun with: -v
==1157==
bin   data0  dev  home  lib64       media  mnt  opt   root  selinux  sys       tcsql.db.idx.pkey.dec  ttserver.pid  var
boot  data1  etc  lib   lost+found  misc   net  proc  sbin  srv      tcsql.db  tmp                    usr
==1157==
==1157== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 5 from 1)
==1157== malloc/free: in use at exit: 28,471 bytes in 36 blocks.
==1157== malloc/free: 166 allocs, 130 frees, 51,377 bytes allocated.
==1157== For counts of detected errors, rerun with: -v
==1157== searching for pointers to 36 not-freed blocks.
==1157== checked 174,640 bytes.
==1157==
==1157== LEAK SUMMARY:
==1157==    definitely lost: 0 bytes in 0 blocks.
==1157==      possibly lost: 0 bytes in 0 blocks.
==1157==    still reachable: 28,471 bytes in 36 blocks.
==1157==         suppressed: 0 bytes in 0 blocks.
==1157== Reachable blocks (those to which a pointer was found) are not shown.
==1157== To see them, rerun with: --leak-check=full --show-reachable=yes


  3、使用示例:对一个使用libevent库编写的“httptest”程序进程检查,返回结果中的“definitely lost: 255 bytes in 5 blocks.”表示发生内存泄漏。
[root@xoyo42 tcsql-0.1]# /usr/local/webserver/valgrind/bin/valgrind --tool=memcheck --leak-check=full ./httptest
==1274== Memcheck, a memory error detector.
==1274== Copyright (C) 2002-2008, and GNU GPL'd, by Julian Seward et al.
==1274== Using LibVEX rev 1884, a library for dynamic binary translation.
==1274== Copyright (C) 2004-2008, and GNU GPL'd, by OpenWorks LLP.
==1274== Using valgrind-3.4.1, a dynamic binary instrumentation framework.
==1274== Copyright (C) 2000-2008, and GNU GPL'd, by Julian Seward et al.
==1274== For more details, rerun with: -v
==1274==
==1274== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 1005 from 2)
==1274== malloc/free: in use at exit: 402,291 bytes in 74 blocks.
==1274== malloc/free: 15,939 allocs, 15,865 frees, 6,281,523 bytes allocated.
==1274== For counts of detected errors, rerun with: -v
==1274== searching for pointers to 74 not-freed blocks.
==1274== checked 682,468,160 bytes.
==1274==
==1274== 255 bytes in 5 blocks are definitely lost in loss record 17 of 32
==1274==    at 0x4A05FBB: malloc (vg_replace_malloc.c:207)
==1274==    by 0x3C1D809BC6: evhttp_decode_uri (http.c:2105)
==1274==    by 0x401C75: tcsql_handler (in /data0/tcsql/cankao/tcsql-0.1/tcsql)
==1274==    by 0x3C1D80C88F: evhttp_get_body (http.c:1582)
==1274==    by 0x3C1D8065F7: event_base_loop (event.c:392)
==1274==    by 0x403E2F: main (in /data0/tcsql/cankao/tcsql-0.1/tcsql)
==1274==
==1274== LEAK SUMMARY:
==1274==    definitely lost: 255 bytes in 5 blocks.
==1274==      possibly lost: 0 bytes in 0 blocks.
==1274==    still reachable: 402,036 bytes in 69 blocks.
==1274==         suppressed: 0 bytes in 0 blocks.
==1274== Reachable blocks (those to which a pointer was found) are not shown.
==1274== To see them, rerun with: --leak-check=full --show-reachable=yes


  检查httptest程序,发现有一处“char *decode_uri = evhttp_decode_uri(evhttp_request_uri(req));”中的“decode_uri”没有被free,再程序处理完成后加上“free(decode_uri);”后,再使用Valgrind检查,结果已经是“definitely lost: 0 bytes in 0 blocks.”。

  [文章作者:张宴 本文版本:v1.0 最后修改:2009.07.16 转载请注明原文链接:http://blog.zyan.cc/ntp_api_bz/]

  NTP(Network Time Protocol)是由美国德拉瓦大学的David L. Mills教授于1985年提出,除了可以估算封包在网络上的往返延迟外,还可独立地估算计算机时钟偏差,从而实现在网络上的高精准度计算机校时,它是设计用来在Internet上使不同的机器能维持相同时间的一种通讯协定。时间服务器(time server)是利用NTP的一种服务器,通过它可以使网络中的机器维持时间同步。在大多数的地方,NTP可以提供1-50ms的可信赖性的同步时间源和网络工作路径。

  网络时间协议(NTP)的详细说明在RFC-1305[Mills 1992]中。RFC-1305对 NTP协议自动机在事件、状态、转变功能和行为方面给出了明确的说明。它以合适的算法以增强时钟的准确性,并且减轻多个由于同步源而产生的差错,实现了准确性低于毫秒的时间服务,以满足目前因特网中路径量测的需要。

  ntp.api.bz 是一组NTP服务器集群,目前有6台服务器,位于上海电信。这项服务是 api.bz 继 http://sms.api.bz 移动飞信免费短信发送接口之后的第二项免费 API 服务。

  客户端设置:

  1、Linux服务器可通过 ntpdate 命令与时间服务器同步(如果没有安装ntp软件,CentOS可以通过“yum install ntp”命令安装):

/usr/sbin/ntpdate ntp.api.bz


  如果想定时执行ntpdate进行时间同步,可以通过crontab来进行:
crontab -e

  输入以下内容,每小时的第19分钟做一次时间同步:
19 * * * * /usr/sbin/ntpdate ntp.api.bz



  2、Windows服务器或个人电脑请用鼠标双击屏幕右下角的时间,按照下图设置:

  点击在新窗口中浏览此图片

  点击“立即更新”就可以马上更新时间,响应速度与成功率要比原有的 time.windows.com 高得多。
  饭否被和谐了,我的微博客由饭否移到美国佬的地盘。被GFW还可以翻墙,总比信息丢失好。

  设置hosts文件:C:\windows\system32\drivers\etc\hosts
引用
128.121.146.228    twitter.com
168.143.162.101    assets1.twitter.com
168.143.162.101    static.twitter.com
168.143.162.101    assets0.twitter.com
168.143.162.101    assets2.twitter.com
168.143.162.101    assets3.twitter.com
168.143.162.101    assets4.twitter.com


  浏览器通过 https://twitter.com/ 访问。

  不设置hosts,则可以通过 http://www.itweet.net/web/ 等网站访问。

  手机可通过 http://dabr.co.uk 访问。

  我的twitterhttps://twitter.com/rewinxhttp://twitter.com/rewinx

  [文章作者:张宴 本文版本:v1.0 最后修改:2009.07.06 转载请注明原文链接:http://blog.zyan.cc/linux_ext3_undelete/]

  环境:CentOS 5.3 x86_64下,/dev/sdb1为数据分区/data0,EXT3文件系统。
  前因:误删了/data0/tcsql/cankao/phpcws-1.5.0/httpcws.cpp文件。由于忘了备份httpcws.cpp文件,重新开发工作量较大,因此只有恢复该文件一条路可走。

  debugfs命令针对EXT2分区还行,但对EXT3分区就帮不上忙了。偶然发现的一款开源软件,解决了我的大忙。该软件下载网址为:
  http://code.google.com/p/ext3grep/

  1、先安装ext3grep软件:
wget http://ext3grep.googlecode.com/files/ext3grep-0.10.1.tar.gz
tar zxvf ext3grep-0.10.1.tar.gz
cd ext3grep-0.10.1
./configure
make
make install


  2、umount /data0分区:
umount /data0

  如果提示busy,先kill正在使用这个目录的进程,再umount:
fuser -k /data0
umount /data0


  3、查询所有Inode,(执行需要几分钟~十多分钟):
ext3grep /dev/sdb1 --ls --inode 2

  点击在新窗口中浏览此图片

  4、逐级查找Inode,看是否能找到httpcws.cpp文件(此步骤也可省略):
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