What is Cache? Understand How It Works

You’ve probably heard of the term “cache” when browsing the web or using apps, but do you know what it really is? In simple terms, cache is a tool that helps your digital devices run faster. It stores data you frequently access so it can be retrieved quickly when you need it, whether it’s a website you visit often or an app you use daily.

In this post, we’ll dive into what cache is, the different types of cache, and how it plays an essential role in boosting the performance of your devices.

Let’s explore!

What is Cache?

In simple words, a cache is a temporary storage space. It keeps a copy of data that you often use. You can think of it as a shortcut. It helps your devices get information quickly without going back to the original source each time.

Take your web browser cache, for example.

When you visit a website for the first time, your browser cache saves some parts of that site. This includes images, logos, and stylesheets.

The next time you visit the same website, your browser can load this cached data more quickly. This makes your browsing experience smoother and faster. Remember, this cached data isn’t permanent. It can be overwritten or cleared when needed. Still, it has a big effect on how fast you use websites and apps.

Cache on Computer

Your computer needs cache to work well. One important type is the CPU cache, which is located right on the processor. The CPU cache saves instructions and data that the CPU uses often and needs to get quickly. Since the CPU cache is closer and much faster than the main memory (RAM), it gives the CPU the needed information almost instantly.

When the CPU wants a piece of data, it first looks in the CPU cache. If it finds what it needs, this is called a cache hit, and the CPU can get it fast. If it doesn't find the data (this is a cache miss), the CPU has to get it from the main memory, which takes more time. This shows how important it is to have a good and properly sized CPU cache for the best computer performance.

Having a larger CPU cache usually means more cache hits and fewer cache misses, leading to a computer system that is faster and more responsive.

Cache on Mobile Apps

Cache is not just for computers; it’s also important for mobile devices. So, what is cache on my phone?

Mobile apps use cache to work better and improve user experience, just like websites do. When you use an app, it saves things like images, icons, and data in its own cache on your device.

Think about a social media app. When you scroll through your feed, the app may keep your friends' profile pictures and shared images in cache. This means that the next time you check their profiles or see their posts, the app does not need to download those images again. This saves you time and data.

By keeping these commonly used elements on your device, mobile apps can load faster and reduce waiting times. This creates a better experience for users.

How Cache Works

As we said before, when your device or app needs to get a piece of data, it first looks in the cache. If the data is there (this is called a cache hit), it can be accessed much quicker than if it comes from the slower main storage. It's like finding something in your pocket instead of looking for it in a big backpack.

If the data isn't in the cache (this is a cache miss), the device will go to the main storage to get it. It often saves a copy in the cache for next time so it can be found quicker. This checking, retrieving, and updating of the cache happens all the time while you use your devices and apps.

Write-Through vs. Write-Back Cache

Cache policies dictate how data is written and managed within the cache memory. Two common policies are write-through and write-back, each with its own advantages and disadvantages in terms of performance and data integrity.

Let's understand them:

• Write-through cache: Data is written to both the cache and the main memory simultaneously. This ensures data integrity as any changes are immediately reflected in both places. However, it can be slightly slower for write operations as it involves writing to two locations.
• Write-back cache: Data is written only to the cache initially. The changes are written to the main memory later, usually when the cache line needs to be replaced. This is faster for write operations, but there is a slight risk of data loss if a power failure occurs before the data is written back to main memory.

The choice between write-through and write-back cache depends on factors like the system's requirements for performance and data integrity.

On-Chip vs. External Cache

Cache can be found in different locations, which affects how fast it is and how well a system works. On-chip cache is on the same chip as the processor (CPU). This closeness means data can be accessed really quickly, making processing much faster. However, on-chip cache is usually small because there’s limited space. So, it mostly keeps the data that is used most often.

External cache is different. It is outside the processor chip and often found on separate memory modules. While external cache is still quicker than getting data from main memory, it is not as fast as on-chip cache. But, external cache can be larger, which lets it hold more data. Many systems use both on-chip and external cache to achieve a good balance of speed and storage. This combination helps improve overall performance.

Cache policies

Managing a cache well means having clear policies that guide how data is used in the cache environment. These policies look at how to place data, how to replace it, and how to keep data consistent. Cache clients, like CPUs, browsers, or applications, work with the cache based on these rules.

An important part of this is the replacement policy. This policy decides which data is removed from the cache when there is no space for new data. Common replacement policies are Least Recently Used (LRU) and Least Frequently Used (LFU). LRU takes out the data that has not been used for the longest time, expecting that data used recently may be needed again. LFU, on the other hand, removes the data that is used the least, assuming that data not accessed often is less important.

Keeping data consistent is also very important, especially when multiple cache clients might use the same data. Cache coherence protocols are used to make sure all clients have the latest version of the data. This helps avoid mistakes and errors.

Types of Cache Memory

There is no single solution for cache. Different types of cache memory are made for specific needs. They are used at different levels in a computing system. Knowing about these types helps you understand how cache improves performance.

The CPU cache is important for fast processing. The browser cache helps make web browsing quicker. Each type serves a unique purpose. For instance, a database cache makes database queries faster. DNS caching helps speed up the process of resolving domain names.

Browser Cache

Web cache, often called browser cache, affects how you browse the internet every day. When you go to websites, your web browser saves some parts of those web pages on your device. This web cache usually includes static content that doesn’t change much, like images, logos, stylesheets, and even some full HTML pages.

By saving this static content, your browser doesn’t have to download the same files from the origin server each time. Next time you visit that website, your browser can load cached content quickly, leading to faster loading times and reduced bandwidth usage. This speeds up browsing and saves data, which is especially useful for mobile devices with limited data plans.

While this is generally useful, there are times when you need to refresh your browser cache.

Database Caching

Database caching aims to make database queries faster. It stores data that people often access in a special memory called cache memory, which is closer to the application. When the application needs to get data, it first looks in the cache. If it finds the data there (this is called a cache hit), the application does not have to query the main database, which takes much longer.

This method works best for data that is used a lot but doesn’t change often. Instead of going back to the database repeatedly, which can take time and involve many steps, the application can get the information quickly from the cache memory.

Using database caching greatly helps application performance. It lowers the stress on the database and makes the whole system work better. This technique is important for applications that need to interact with the database often, helping them get the needed data more quickly.

What Happens if the Cache is Removed?

Cache is important for improving user experience and application performance. However, if you remove it, it does not mean everything will go wrong. It just means your device or application will have to get data from a slower storage layer, at least for a while. This can cause some changes that you might notice.

At first, you may see slower loading times, particularly for websites and apps that you use often, since the cached data has to be rebuilt. But this is usually just a short-term issue. As you keep using your device or application, the cache will fill up again with the data you access the most, and the performance will slowly get better.

Slower Load Times (Initially)

Slower load times can happen at first when there is a cache miss. This means the browser must access data directly instead of using cached data. This situation can hurt the user experience because it does not use cached data from the memory cache or browser cache, which results in longer retrieval times.

By making cache memory better and aiming for a higher cache hit rate, applications can run more efficiently and improve overall performance. It is important to understand how cache works. This knowledge helps manage data retrieval, leading to faster response times and better application performance.

Fixes Website Issues

Ironically, clearing your browser cache can slow down your browsing for a bit, but it can help fix some confusing website problems. Your browser cache sometimes keeps old or bad cached data. This can cause web pages not to load right, lead to formatting problems, or even crash websites.

When you clear your browser cache on Mac or Windows, you make your browser get new data from the websites you use. This can help fix problems that come from outdated cached data. If a website has changed, clearing your cache makes sure you see the latest version.

However, remember that clearing your browser cache will log you out of websites. You will need to re-enter your login info.

Free Up Storage Space

Cached data is usually small and meant to be temporary. However, it can build up over time, especially if you use the internet or apps a lot. Clearing your cache on different apps and devices can free up a good amount of storage space. This is especially helpful for mobile devices that have limited space.

When you clear cached data, you are just getting rid of files that you don't need right away. Your device or apps can always download or recreate these files later if necessary. Clearing your cache won't remove important files, saved passwords, or essential information. Still, it's a smart idea to back up your important data regularly, just in case.

Updated Content

Another good thing about removing cache is that it makes your device or app get the latest content from the origin server. This matters a lot for websites or web applications that change their content often. When you go to a website for the first time or after clearing your cache, your device asks for the newest version of the content from the server.

The server gives the updated content back, and it is saved in your cache for future requests. But if your cache data is old, your device might keep showing the older version until the cache goes away or gets cleared by you.

How To Clear Cache?

The way to clear your cache can vary depending on the web browser you use. However, in general, the steps are as follows:

1. Open your default browser. Click the three vertical dots in the top right corner.
2. Go to "Settings" and then "Delete browsing data."
3. Choose the time range for which you want to clear the cache. You can pick options like "Last hour," "Last 24 hours," or "All time."
4. Check the boxes for "Cookies and other site data" and "Cached images and files."
5. Click "Clear data."

Keep in mind that clearing your cache will log you out of websites, so you may need to log back in with your username and password.

Frequently Asked Questions

How does clearing cache improve device performance?

Clearing the cache can make your device work better. It frees up cache memory that can get clogged. This helps your device respond faster and run smoother. On mobile devices, it can even help the battery life. Less processing power is needed to access data, which allows the battery to last longer.

Can cache size affect overall system speed?

Yes, the size of the cache can impact overall performance. A larger cache can hold more data. This leads to a higher cache hit rate. With a higher cache hit rate, the system runs faster, especially for demanding application workloads.

Is it safe to delete cache, and what are the consequences?

Yes, it is usually safe to delete your cache. Doing this won't lead to data loss. You may notice a short change in user experience, like having to log back into some websites. However, web content will reload from the content delivery network.

If you also delete your cookies, you may need to re-enter preferences or login details on websites.

How often should cache be cleared for optimal performance?

You don't need a set schedule, but it’s a good idea to clear your cache every few weeks. This can help keep your device running well. If you're worried about battery power on mobile devices or having trouble with web applications, you can clear it more often.

What's the difference between cache memory and RAM?

Cache memory is smaller and quicker than RAM. It holds data that the central processing unit (CPU) uses often. This way, it serves as a link between the CPU and the bigger, slower main storage, which is RAM.

Will clearing the cache delete pictures?

No, clearing the cache will not remove your pictures. It mainly gets rid of temporary files and data to create more space. Your pictures are saved separately on your device.