The Redis Kernel understands

First, Memory elimination

Second, object reference counter

1. Redis Key-"value" is stored in Redisobject, when the object is initialized, RefCount = 1; (Figure 1)

2, when the client uses get, RefCount +1, when released Refcount-1;

3. When using Del, refcount-1

4. If RefCount = 0, remove from memory

Figure 1

Third, the elimination of outdated data

Redis does not check whether data is out of date every moment because it is inefficient. The Redis cleanup expiration data is carried out in two phases, the first phase in the timer (Servercron, the action to clean up the expired data every 100ms), and the second stage when the user obtains the data.

The timer only randomly deletes some outdated data, it is impossible to completely delete all the outdated data.

The Redis Kernel understands