Why redis is single-threaded

The reasons why redis is single-threaded: 1. Single-threaded does not require the performance consumption of various locks; 2. Single-threaded multi-process cluster solution; 3. Single-threaded avoids unnecessary context switching and race conditions. , and there is no switching caused by multiple processes or threads that consumes the CPU.

Simple analysis:

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Redis It is a memory-based operation. The CPU is not the bottleneck of Redis. The bottleneck of Redis is most likely the size of the machine memory or the network bandwidth. Because single-threading is easy to implement and the CPU will not become a bottleneck, it is logical for redis to adopt a single-threaded solution.

Detailed reason introduction:

1. No performance consumption of various locks is required

The data structure of Redis is not all simple Key-Value, but also list and hash Such complex structures may perform very fine-grained operations, such as adding an element to the end of a long list, adding or deleting an object from a hash. These operations may require adding a lot of locks, resulting in a greatly increased synchronization overhead.

In short, in the case of a single thread, there is no need to consider various lock issues. There is no locking and releasing lock operations, and there is no performance consumption caused by possible deadlocks.

2. Single-threaded multi-process cluster solution

The power of single-thread is actually very powerful, and the efficiency of each core is also very high. Multi-threading can naturally have a higher performance limit than single-threading. , but in today's computing environment, even the upper limit of single-machine multi-threading often cannot meet the needs. What needs to be further explored is multi-server clustering solutions, in which multi-threading technology is still not available.

3. CPU consumption

Uses a single thread to avoid unnecessary context switching and competition conditions, and there is no CPU consumption due to switching caused by multi-process or multi-threading. But what if the CPU becomes the bottleneck of Redis, or you don’t want other CPU cores of the server to be idle?

You can consider starting several more Redis processes. Redis is a key-value database, not a relational database, and there are no constraints between data. As long as the client distinguishes which keys are placed in which Redis process, it will be fine.

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