Direct mapping is a simple method of storing information in a cache for easy access. Cached data is constantly overwritten, and the hit rate determines how often data is found in the cache. However, direct mapping has a lower success rate than other models due to frequent overwriting.
Direct mapping is a method of storing information for easy access on a computer. Recently used information is stored in a cache so that your computer can find the information quickly the next time it’s needed. In computer programming, a cache is a small section of random access memory (RAM) that is set aside for the purpose of easy data retrieval. With direct mapping, each data in memory is assigned a space in the cache, which it shares with other data. Cached data is constantly being overwritten as new data is needed.
A cache is organized in rows. Each row is only large enough to store one block of data and a tag to identify where the data came from. When a user requests data, the computer first scans the cache to see if the information is there. If so, the information is returned to the user. This is known as a cache hit, which is faster than fetching the data from its original location.
The percentage of requests that result in hits in the cache is called the hit rate. If the data requested by the user is not in the cache, the computer will find it in memory. A copy of the data will be cached so it can be found quickly the next time the user requests it, in theory increasing the success rate. All of this happens behind the scenes. The user doesn’t know if the received data is from cache or memory.
Direct mapping is a method of deciding where memory blocks will be stored in the cache. Each block of memory is assigned a specific row in the cache. Since the cache is smaller than memory, multiple blocks will share a single row in the cache. If a line is already full when a new block is to be written, an old block will be overwritten.
While direct mapping is a very simple and easy way to design a cache, it has some problems. If a program continually accesses multiple data blocks that share the same row in a direct mapping cache, the row will be rewritten often. This results in a lot of errors because the data the computer needs is less likely to be the data that is actually in that cache line at the moment. So direct mapping has a lower success rate than other cache mapping models.
Protect your devices with Threat Protection by NordVPN
