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This article is to share with you about the principles of using cache to improve system performance. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

The use of cache to improve system performance is based on the locality principle of the program. When CPU needs to read data, first look in cache to see if there is anything you need, and if so, read it directly from cache. If most of the content that CPU needs to access can be found in cache (called access hits), system performance can be greatly improved.

The operating environment of this tutorial: windows7 system, Dell G3 computer.

The use of cache to improve system performance is based on the locality principle of the program. According to the locality principle, the contents with high access probability in the main memory are stored in cache. When CPU needs to read data, first find out if there is anything needed in cache, if so, read it directly from cache; if not, read the data from main memory and send it to CPU and cache at the same time. If most of the content that CPU needs to access can be found in cache (called access hits), system performance can be greatly improved.

The average storage cycle of the system is closely related to the hit rate, and the improvement of the hit rate can bring great improvement in performance even if it is very small.

After the CPU sends out the memory access request, the memory address is first sent to the cache controller to determine whether the required data is already in the cache, and if it is hit, the cache is accessed directly. This process is called cache address mapping. The common mapping methods are direct mapping, associative mapping and group associative mapping.

After an access miss occurs in the cache memory, the corresponding data should be read into both CPU and cache. However, after the cache is full of data, the new data must eliminate some of the old data in the cache. The most commonly used elimination algorithms are random knockout, first-in, first-out (FIFO) and recent least use knockout (LRU).

Because you need to ensure that the data cached in cache is consistent with the content in main memory, the write operation of cache is more complex than read operation, and the following methods are commonly used:

(1) write direct (write through). When cache is to be written, the data is also written back to the main memory, sometimes referred to as write-through.

(2) write back (write back). After CPU modifies a row of cache, the corresponding data is not immediately written to the main memory unit, but is written back to the main memory when the row is eliminated from the cache.

(3) marking method. Set a significant bit for each data in the cache. When the data enters the cache, the effective position is 1; when the CPU wants to modify the data, it simply writes it to the main memory and clears the effective bit 0 at the same time. When you want to read data from cache, you need to test its significant bits: if it is 1, fetch the number directly from cache, otherwise, fetch the number from main memory.

Thank you for reading! This is the end of the article on "what is the basis for using cache to improve system performance". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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