# 调优

## 调优的目的：

1. 根据不同的角色调优的方法是不一样的
2. 找到性能瓶颈以及缓解这个瓶颈（CPU，内存，IO调度、网络、使用的应用程序）
3. 通常做两种调优：

    response time:  Web服务器，用户感受度好

    throughput:     文件服务器，拷贝的速度

## 性能调优的效率问题：

### 业务级调优

尽量在业务级调，效果最明显

例如： 网站一定要使用Apache吗? 例如：将原有的调度器由LVS换成F5-BigIP 例如：能否禁用一些不必要的服务如蓝牙、smart card，makewathis, updatadb

### 应用级调优

NFS，Samba，Apache、Nginx、MySQL、Oracle、LVS本身调优\
对于日志的处理： 只要有日志产生，就会存盘fsync()，可以调整记录的日志等级或延后日志写，从而避免大量的I/O操作 kernel级调优 最后的希望，kernel调优具有普遍性

自上往下，效果越来越不明显


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