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67 lines
1.9 KiB
Markdown
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如何更改IO调度器
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==================================
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Linux IO 调度器，IO调度器也叫磁盘调度器。Linux IO调度器的机制主要是控制块设备的请求队列：确定队列中哪些IO的优先级更高以及何时下发IO，以此来减少磁盘寻道时间，从而提高系统的吞吐量。
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目前Linux上有如下几种IO调度算法：
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1. noop - 通常用于内存存储的设备.
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2. cfq - 绝对公平调度器. 进程平均使用IO带宽.
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3. Deadline - 每一个IO，都有一个最晚执行时间.
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4. Anticipatory - 启发式调度，类似Deadline算法，但是引入预测机制提高性能.
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查看设备当前的IO调度器：
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```
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# cat /sys/block/<Disk_Name>/queue/scheduler
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```
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假设磁盘名称是 /dev/sdc:
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```
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# cat /sys/block/sdc/queue/scheduler
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noop anticipatory deadline [cfq]
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```
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### 如何改变硬盘设备I/O调度器
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使用如下指令：
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```
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# echo {SCHEDULER-NAME} > /sys/block/<Disk_Name>/queue/scheduler
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```
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比如设置 noop 调度器:
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```
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# echo noop > /sys/block/sdc/queue/scheduler
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```
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以上设置重启后会失效，要想重启后配置仍生效，需要在内核启动参数中将 "elevator=noop" 写入 /boot/grub/menu.lst:
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#### 1. 备份 menu.lst 文件
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```
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cp -p /boot/grub/menu.lst /boot/grub/menu.lst-backup
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```
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#### 2. 更新 /boot/grub/menu.lst
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将 "elevator=noop" 添加到文件末尾，比如:
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```
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kernel /vmlinuz-2.6.16.60-0.91.1-smp root=/dev/sysvg/root splash=silent splash=off showopts elevator=noop
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```
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--------------------------------------------------------------------------------
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via: http://linuxroutes.com/change-io-scheduler-linux/
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作者：[UX Techno][a]
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译者：[honpey](https://github.com/honpey)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://linuxroutes.com/change-io-scheduler-linux/
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