主题：java性能优化权威指南 pdf
版本：英文版 Java Performance Tuning
忽略：（0~24页）Performance+Acknowledge
1、Strategies, Approaches, and Methodologies.
三层境界：
1.i don't know what i don't know.
2.i know what i don't know.
3.i already know what i need to know.
两种方法：
Two different performance tuning approaches, top down and buttom up.
2、软件development过程中缺乏performance的analysis和testing。
1.Software development：analysis, design, coding and testing. but give little a attention to performance and scalability.
2.Today many application under development utilize automated build and test procedures. it should integrating performance testing into automated build processes testing system.
3、Two Approaches, Top Down and Bottom up.
1.top down, the most common approach utlized for performance tuning.step one:Monitoring the application while it is running under a load of particular interest.(Monitoring activity include observing OS, JVM, Java EE container)
2.bottom up, it is improve the performance of an application on one platform relative to another platform(diffreenes exists in the underlying CPU, CPU architecture, number of CPUs).the focus of the bottom up approach is usually to improve the utilization of the CPU without making changes to the application.
