> For the complete documentation index, see [llms.txt](https://moluo.gitbook.io/notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://moluo.gitbook.io/notes/bian-cheng-xue-xi/shu-ju-ku/redis/2.4-dan-xian-cheng.md).

# 2.4单线程

## 单线程架构

redis在一个瞬间只会执行一条命令

## redis使用单线程为什么还这么快？

1. 纯内存，一条命令在内存中的响应时间大概是100ns
2. 非阻塞IO
3. 避免线程切换和竞态消耗

## 使用redis的注意事项

1. 一次只执行一条命令
2. 拒绝长（慢）命令，包括keys、flushall、flushdb、slow lua script、mutil/exec、operate big value（collection）
3. 其实不是单线程

   fysnc file descriptor或close file descriptor是另外启动线程来执行的


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