经过性能分析来肯定什么缘由致使CPU繁忙是平常工做中长作的事情，这每每会涉及到栈性能分析。经过按期采样的方式来肯定哪些代码是致使CPU繁忙的缘由是一个比较粗糙的方法。一个更好的方式是建立一个定时中断来收集程序运行时的计数，函数地址，甚至整个堆栈回溯，最后打印为咱们可阅读的报告.咱们经常使用的性能分析工具备oprofile,gprof,dtracesystemtap 等
1）安装systemtapnginx
1)安装必要组件c++
sudo yum install gcc gcc-c++ elfutils-develgit
2)下载安装systemtapgithub
wget https://sourceware.org/systemtap/ftp/releases/systemtap-2.6.tar.gz
tar -xvf systemtap-2.6.tar.gz
cd systemtap-2.6/
./configure --prefix=/opt/stap --disable-docs \
--disable-publican --disable-refdocs CFLAGS="-g -O2"
make -j8 # the -j8 option assumes you have about 8 logical CPU cores available
sudo make install
3)建立软连接
ln -s /opt/systemtap/bin/stap /usr/sbin/stap
4)安装debug包
uname -r
而后去http://debuginfo.centos.org站点寻找与内核相匹配的debug packages
wget http://debuginfo.centos.org/7/x86_64/kernel-debuginfo-3.10.0-229.20.1.el7.x86_64.rpmweb
wget http://debuginfo.centos.org/7/x86_64/kernel-debuginfo-common-x86_64-3.10.0-229.20.1.el7.x86_64.rpmcentos
检查内核debug包是否已安装成功浏览器
# rpm -ivh kernel-debuginfo-($version).rpm # rpm -ivh kernel-debuginfo-common-($version).rpm # rpm -ivh kernel-devel-($version).rpm
rpm -Uhv kernel-debuginfo-*rpm
5)#测试systemtap安装成功否：
stap -ve'probe begin { log("hello world") exit() }'
[root@codis-1 webserver]# stap -ve 'probe begin { log("hello world") exit() }'svg
Pass 1: parsed user script and 111 library script(s) using 217244virt/34632res/3108shr/32088data kb, in 220usr/30sys/249real ms.函数
Pass 2: analyzed script: 1 probe(s), 2 function(s), 0 embed(s), 0 global(s) using 218040virt/35424res/3204shr/32884data kb, in 10usr/0sys/8real ms.工具
Pass 3: translated to C into "/tmp/stapYifYaO/stap_ccb88aee9cb0e924010653f05c104a62_1073_src.c" using 218040virt/36028res/3744shr/32884data kb, in 0usr/0sys/0real ms.
Pass 4: compiled C into "stap_ccb88aee9cb0e924010653f05c104a62_1073.ko" in 8410usr/1750sys/11973real ms.
Pass 5: starting run.
hello world
Pass 5: run completed in 10usr/40sys/422real ms.
[root@codis-1 webserver]#
6）火焰图绘制
下载ngx工具包，该工具包便是用perl生成stap探测脚本并运行的脚本，若是是要抓Lua级别的状况，请使用工具 ngx-sample-lua-bt,若是是要抓Luajit级别的状况，请使用工具 ngx-lj-lua-bt,
#cd tools
# git clone https://github.com/openresty/stapxx.git
39386为nginx worker ,必定要在cpu多高的时候运行该命令
./samples/lj-lua-stacks.sxx --skip-badvars -x 39386 > a.bt
cd tools
git clone https://github.com/brendangregg/FlameGraph.git
/data/webserver/tools/FlameGraph/stackcollapse-stap.pl a.bt > a.cbt
/data/webserver/tools/FlameGraph/flamegraph.pl a.cbt > flame.svg
而后用浏览器打开flame.svg，来分析影响性能的函数便可