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What is cached data and caching?

The computer, alas, does not immediately execute commands,which receives from people. To speed up this process, a number of tricks are used, and an honorable place among them belongs to caching. What it is? What are the cached data? How does this process actually happen? What is the cached data in the Samsung smartphone, for example, and they differ from something that is in the computer? Let's get to the answers to these questions.

What is a cache?

what is cached data
This is the name of the intermediate buffer, whichprovides quick access to information, the probability of which is the highest. All the data is contained in it. An important advantage is that you can extract all the necessary information from the cache much more quickly than from the original storage. But there is a significant drawback - size. Cached data is used in browsers, hard drives, CPUs, Web servers, WINS and DNS services. The basis of the structure are record sets. Each of them is associated with a certain element or data block, which is a copy of what is in the main memory. The records have an identifier (tag), with the help of which the correspondence is determined. Let's look at a slightly different point of view: what is the cached data in the Samsung phone or other manufacturer? Are they different from those that are created in the computer? From a principled point of view - no, the difference is only in the amount.

Process of use

What is cached data on android
When the client (they were listed above)requests data, the first thing the computer does is examine the cache. If there is a necessary record in it, then it is used. In these cases, a hit occurs. Periodically, data from the cache is copied to the main memory. But if the desired record was not found, then the content in the base repository is searched. All the information is transferred to the cache, so that it can then be accessed more quickly. The percentage where requests are crowned with success is called the level or hit ratio.

Updating the data

When using, say, a web browsera local cache is checked to find a copy of the page. Given the limitations of this type of memory, when a miss occurs, it is decided to discard some information to free space. To solve what exactly will be replaced, various wipe algorithms are used. By the way, if we talk about what cached data is on Android, then in mass they are used to work with pictures and application data.

Write policy

what is cached data in smarphone samsung
During the modification of the contents of the cache, the data is also updated in the main memory. The time delay that occurs between the input of information depends on the recording policy. There are two main types:

  1. Immediate recording. Each change is synchronously stored in the main memory.
  2. Deferred or reverse recording. Updating the data is carried out periodically or upon request from the client. To track whether a change was made, use a symptom with two states: "dirty" or changed. In case of a miss, two calls directed to the main memory can be made: the first is used to write down data that has been changed from the cache, and the second is to read the required item.

It may also be that the information in thethe intermediate buffer becomes irrelevant. This happens when you change the data in the main memory without making any adjustments to the cache. For the consistency of all editing processes, coherence protocols are used.

Modern Challenges

What is cached data in the smartphone's memory?
With increasing frequency of processors andIncreasing the performance of memory has a new problematic place - the limited interface of data transmission. What can a knowledgeable person notice? The cache memory is very useful if the frequency in the RAM is less than in the processor. Many of them have their own intermediate buffer to reduce the access time to RAM, which is slower than registers. In CPUs that support virtual addressing, they often place a small but very fast address translation buffer. But in other cases, the cache is not very useful, and sometimes only creates problems (but this is usually in computers that have been modified by a layman). By the way, when talking about what cached data is in the memory of a smartphone, it should be noted that because of the small size of the device, it is necessary to create new miniature implementations of the cache. Now some phones boast parameters like those of advanced computers ten years ago - and what a difference in their size!

Synchronization of data between different buffers

The cache is useful when there is one, but how to maintain the effectiveness of this technology, if there are many? This problem is solved by the coherence of the buffer. There are three options for data exchange:

  1. Inclusive. The cache can behave as you like.
  2. Exclusive. Developed for each specific case.
  3. Non-Exclusive. The standard of wide distribution.

Levels of caching

what is the cached data in the smartphone
Their number is usually equal to three or four. The larger the memory level, the more volume and slower:

  1. L1 cache. The fastest level of the cache is the first. In fact, it is part of the processor, because it is located on the same chip and belongs to the functional blocks. It is usually divided into two types: a cache of instructions and data. Most modern processors without this level do not work. This cache functions on the processor frequency, so every cycle can access it.
  2. L2 cache. Usually it is located together with the previous one. It is a memory of separate use. To find out its value, it is necessary to divide all the volume given for data caching into the number of cores that is in the processor.
  3. L3 cache. Slow, but the biggest dependent cache. Usually more than 24 MB. Used to synchronize data that comes from different L2 caches.
  4. L4 cache. The use is justified only for high-performance multiprocessor mainframes and servers. It is implemented as a separate microcircuit. If you ask a question about what data caching is in a Samsung smartphone and look for this level in it, I can say that for 5 years you just hurried.

Cache associativity

This is a fundamental characteristic. The associativity of cached data is necessary for mapping logical segmentation. It, in turn, is necessary because the sequential search of all available lines takes dozens of cycles and reduces all advantages to it. Therefore, a rigid binding of RAM cells to the cache data is used, to shorten the search time. If we compare the intermediate buffers, which have the same volume, but different associativity, then the one with the larger one will work less quickly, but with significant specific efficiency.


what is the cached data in the phone samsung
As you can see, the cached data for certainallows your computer to operate more quickly. But, alas, there are still quite a few aspects over which you can work for a long time.

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