1.Jprofile找到程序性能的瓶颈
2.需要很长时间完成的过程由单线程转多线程或线程池。假如是IO之类的问题(普遍IO是系统的瓶颈),采用NIO即rector模式处理
3.大量小文件压缩后存入内存,定量写入硬盘。大量中间变量存入内存,或序列化压缩后存入内存，后解压反序列化调用
4.使用Queue进行不同过程的缓冲
5.Linux下普遍有打开文件个数限制，消除1024限制:ulimit -n 8192
6.JVM普遍内存限制，消除内存限制:增加运行参数 -Xms20m -Xmx200m
另:
1.如何执行jar中某个类的main方法: java -cp test.jar com.acosys.clawer.GetContent
2.如何让java程序在linux后台运行: nohup … &
3.如何查看linux后台运行的nohup程序列表: jobs
4.后台FTP上传下载工具: ncftpget ncftpput
5.如何查找linux后台程序列表 ps aux | grep …
6.强行终止linux程序: kill -9 …
7.查某文件夹下文件数目: ls -l |grep “^-”|wc -l
8.执行多个依赖库的java程序:java -cp nutch-1.0.jar:commons-logging-1.0.4.jar:hadoop-0.19.1-core.jar:xerces-2_6_2.jar org.apache.nutch.tools.DmozParser content.rdf.u8 > domz/urls
最近在做world wide数据信息的分析，偶然发现这个不错的工具。
The default collation in mysql is not always utf-8. Because the company of mysql localed in Sweden, so the encoding or collation is latin1_swedish_ci by default. You should change this feature after you installed the mysql DB server. But If you have operated your web site for a long time, then you want to update your site for reasons. There are lots of data existed in Mysql in the encoding latin or other not UTF8. How to change the encoding or Collation to UTF-8 ?
