systemtap初探

喜欢ヅ旅行 2022-06-11 23:30 161阅读 0赞

Solaris上有Dtrace可以对如Oracle,MySQL进行调试，那Linux也有，那就是systemtap。如Oracle和MySQL出了问题，发现是system的问题，那只能等官方的说法，很被动。如果有这个工具，那就能挖得更深一点，对解决问题很有帮助。

内核引入了一种Kprobe机制，可以用来动态地收集调试和性能信息的工具，是一种非破坏性的工具，用户可以用它跟踪运行中内核任何函数或执行的指令等。systemtap 是利用Kprobe 提供的API来实现动态地监控和跟踪运行中的Linux内核的工具，相比Kprobe，systemtap更加简单，提供给用户简单的命令行接口，以及编写内核指令的脚本语言。

安装这个功能颇费周折，需要安装两个rpm。要想绕过坑，就要执行stap-prep,看下系统需要安装那个版本。  
\[root@localhost shm\]\# stap-prep  
Need to install the following packages:  
kernel-debuginfo-2.6.32-431.el6.x86\_64  
...........................................  
  
  可以到http://debuginfo.centos.org/6/x86\_64/下找到相应的版本，kernel-debuginfo-common-x86\_64-2.6.32-431.el6.x86\_64.rpm这个有260M。  
\[root@localhost shm\]\# rpm -ivh kernel-debuginfo-common-x86\_64-2.6.32-431.el6.x86\_64.rpm  
Preparing...                \#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\# \[100%\]  
   1:kernel-debuginfo-common\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\# \[100%\]  
  
  安装kernel-debuginfo-2.6.32-431.el6.x86\_64.rpm这个也是，如果发现版本不对，系统会提示你需要安装的版本。  
\[root@localhost shm\]\# rpm -ivh kernel-debuginfo-2.6.32-431.el6.x86\_64.rpm  
error: Failed dependencies:  
        kernel-debuginfo-common-x86\_64 = 2.6.32-431.el6 is needed by kernel-debuginfo-2.6.32-431.el6.x86\_64  
          
\[root@localhost shm\]\# rpm -ivh kernel-debuginfo-2.6.32-431.el6.x86\_64.rpm  
Preparing...                \#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\# \[100%\]

1:kernel-debuginfo       \#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\# \[100%\]

测试一下是否安装成功

\[root@localhost mysql-5.6.14\]\# stap -v -e 'probe vfs.read \{printf("read performed\\n"); exit()\}'  
Pass 1: parsed user script and 112 library script(s) using 206604virt/34432res/3212shr/31532data kb, in 30usr/460sys/607real ms.  
Pass 2: analyzed script: 1 probe(s), 1 function(s), 4 embed(s), 0 global(s) using 303212virt/132016res/4244shr/128140data kb, in 1180usr/1420sys/5393real ms.  
Pass 3: translated to C into "/tmp/stapOq9UI9/stap\_de5b8012cef23568586d0744abf80b8d\_1625\_src.c" using 303212virt/132372res/4600shr/128140data kb, in 0usr/0sys/7real ms.  
Pass 4: compiled C into "stap\_de5b8012cef23568586d0744abf80b8d\_1625.ko" in 1250usr/600sys/2528real ms.  
Pass 5: starting run.  
read performed  
Pass 5: run completed in 10usr/20sys/337real ms.

测试一下，想知道5s探针一下top 20系统命令。  
systemtap\_t.sh  
\#!/usr/bin/env stap  
\# This script continuously lists the top 20 systemcalls on the system  
\#  
global syscalls  
  
function print\_top () \{  
        cnt=0  
        log ("SYSCALL\\t\\t\\t\\tCOUNT")  
        foreach (\[name\] in syscalls-) \{  
                printf("%-20s\\t\\t%5d\\n",name, syscalls\[name\])  
                if (cnt++ == 20)  
                        break  
        \}  
        printf("--------------------------------------\\n")  
        delete syscalls  
\}  
  
probe kernel.function("sys\_\*") \{  
        syscalls\[probefunc()\]++  
\}  
  
\# print top syscalls every 5 seconds  
probe timer.ms(5000) \{  
        print\_top ()  
\}  
  
\[root@localhost root\]\# stap  systemtap\_t.sh  
SYSCALL                         COUNT  
sys\_times                         100  
sys\_poll                           56  
sys\_read                           42  
sys\_restart\_syscall                34  
sys\_ppoll                          28  
sys\_rt\_sigprocmask                 15  
sys\_select                         11  
sys\_close                           5  
sys\_munmap                          5  
sys\_epoll\_wait                      4  
sys\_fcntl                           4  
sys\_write                           4  
sys\_open                            4  
sys\_newfstat                        4  
sys\_mmap                            4  
sys\_mmap\_pgoff                      4  
sys\_wait4                           3  
sys\_alarm                           3  
sys\_rt\_sigpending                   3  
sys\_nanosleep                       3  
sys\_setresuid                       2  
\--------------------------------------  
  
https://sourceware.org/systemtap/ftp/releases 源码下载。