The situation when the once-quick Xiaomi Redmi Note 9 suddenly begins to hang, familiar to many owners. Smartphone released as a sturdy middle-class, over time can show signs of “fatigue”: long launch of applications, jerks when scrolling tape or delays in typing. This is annoying, because the device must work smoothly.
The reasons for the slowdown of the operating system can be software-related, memory overflow, or hardware-related, physical wear and tear of components. Understanding the nature of the problem is the first step to solving it, and often it is enough to perform a competent optimization to return the gadget to its former friction.
In this article, we will discuss in detail why the Xiaomi Redmi Note 9 is slowing down, and provide step-by-step troubleshooting instructions. We will touch on system settings, file system work and features of the MIUI shell, which are most often the culprits of lags.
Internal memory overflow and system cache
One of the most common reasons Redmi Note 9 starts to run slowly is the critical filling of the built-in storage, where the free space is less than 10-15% of the total, the file system has difficulty writing temporary files and caching data, leading to noticeable delays in the interface.
The Android operating system uses free space for swaps and temporary operations. If the memory is filled to the end, the processor has to spend resources on constant defragmentation and search for free blocks, as a result, the user observes the friezes and twitches of the screen.
To clean up, you need to remove unnecessary files, duplicate photos and cache of heavy applications such as messengers and social networks, and pay special attention to the Download folder and browser cache, which often grow to gigabytes.
- 🗑️ Remove old videos from the gallery or transfer them to a cloud server/computer.
- 📱 Clear the cache of garbage files through the standard application "Security".
- 💬 In WhatsApp and Telegram settings, delete automatically saved media files.
- 📲 Deinstall apps you haven’t used in the last 3 months.
⚠️ Note: Do not delete system files from Android root folders unless you are sure of their purpose – this can lead to unstable system operation.
☑️ Cleaning up memory
Problems with RAM (RAM)
The Xiaomi Redmi Note 9 comes with different RAM configurations, but even 6GB may not be enough with active multitasking.The MIUI shell is known for its gluttony to RAM resources. When physical memory runs out, the system begins to actively use virtual memory on the internal drive, which is much slower.
Background processes, geolocation services, and data synchronization can stealthily eat up available resources. The user may not notice running applications, but they continue to consume energy and memory, causing a general slowdown in the device, especially when switching between heavy games or applications.
To solve the problem, you need to limit background activity. Modern versions of Android and MIUI have built-in controls, but they are often not enough. Manual setting allows you to significantly offload RAM and speed up the response of the system.
You can use the memory extension feature if it's available in your firmware version, and it allows you to use some of the internal storage as an addition to RAM, which helps keep more applications open.
- 🚀 Close all background apps through the recent task menu.
- 🛑 Turn off auto-run for rarely used programs in settings.
- ⚙️ Limit background activity in the "Applications" section" → "Permits".
- 🔄 Regularly reboot your smartphone to reset accumulated errors in the RAM.
What is Memory Extension?
Processor overheating and trottling
The Snapdragon 730G processor in the Redmi Note 9 is very efficient, but at high loads it is prone to heating. When the crystal temperature reaches critical values, a protective mechanism called trottling is activated. The system forcibly reduces the clock speed of the processor to avoid overheating and damage to components.
Visually, this is manifested in a sharp drop in FPS in games, long application launches and lags, even in simple tasks like typing. Most often, overheating occurs during charging, when using a navigator or in hot weather. A thick case can also interfere with normal heat sink.
To lower the temperature, it is recommended to remove the protective case during resource-intensive tasks, and it is also worth checking whether any film that blocks heat removal is stuck to the screen, or whether the speaker is clogged with dust.
If the phone is warming up in plain, it may be the "curved" app that puts a strain on the CPU in the background. Check the battery usage statistics to find the culprit.
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Use lightweight transparent perforated cases for better cooling, especially if you play games frequently or shoot 4K videos.
Impact of MIUI Updates and Animations
Users often notice that the phone started to brake immediately after the system update. Newer versions of MIUI can be optimized for more powerful hardware, and on the Redmi Note 9 they can work harder.
The visual interface also plays a role. Beautiful but heavy transition animations put a strain on the graphics accelerator. If you value speed over beauty, it makes sense to turn off or speed up animations in the developer settings.
To access hidden settings, you need to activate developer mode, and this is done by repeatedly clicking on the build number in the About section, and then a new item will appear in the menu where you can find zoom options.
Changing the animation scale from 1x to 0.5x or completely shutting down creates the illusion of faster operation of the device.
| Animation parameter | Standard value | Recommended value | The effect |
|---|---|---|---|
| Window animation | 1x | 0.5x or Off | Acceleration of opening/closing applications |
| Animation of transitions | 1x | 0.5x or Off | Quick switching between screens |
| Duration of animation | 1x | 0.5x | A general sense of speed |
Database fragmentation and storage wear
Over time, files on the internal drive of a smartphone are written and deleted chaotically, which leads to fragmentation of the file system. Although modern protocols (UFS 2.1 in Redmi Note 9) are less susceptible to this effect than older eMMCs, the problem still exists, especially when memory is more than 80% full.
In addition, memory cells have a limited rewrite life; over time, read and write speeds can fall, which directly affects the speed of loading the OS and applications; and severe fragmentation causes the memory controller to work harder, consuming the device’s life.
Android's built-in tools periodically optimize storage, but in cases of severe slagging, this may not be enough, and sometimes the only way out is a complete reset that rewrites the file table clean.
It is important to avoid a situation where the memory is full, and leave at least 3-5 GB of free space for normal operation of the memory controller and the algorithms of leveling wear.
⚠️ Warning: A sharp drop in recording speed may indicate nearing end-of-life state of the drive. If the phone is slowing down even after resetting, the physical wear of the board may be a problem.
Third-party applications and viruses
Installing apps from unreliable sources is a surefire way to slow down a smartphone. Malware, cryptocurrency miners, or ad modules can covertly load the processor and network, and even legitimate Google Play apps can contain aggressive advertising or poorly optimized code.
Especially dangerous are the “cleaners”, “accelerators” and antiviruses from unknown developers. Paradoxically, they often slow down the system more than they help, constantly hanging in memory and scanning files. Xiaomi’s standard tools are enough for system hygiene.
Check the list of installed applications. If you see programs with strange names, no icons, or those that you don't remember installing, delete them immediately. It's also worth checking the access rights: why would a flashlight access contacts or geolocation?
Use Google Play Protect to scan your device for threats. It's a basic but effective tool built into Android.
- 🛡️ Check the full version through Google Play Protect.
- 🚫 Remove all cleaner apps and memory boosters.
- 🔍 Check the list of device administrators in the security settings.
- 📉 Track applications with high battery consumption in the background.
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The most effective way to deal with software debris and viruses is to completely reset to factory settings (Hard Reset), but remember to back up data.
Hardware limitations and battery wear
Remember, the Redmi Note 9 is a device that was released a few years ago, and today's apps and web pages are getting heavier, requiring more processing power, and what worked smoothly a year ago can now be causing strain on the CPU's limits.
The state of the battery is also important, and if the battery is worn out and cannot deliver the required current under load, the system can artificially limit performance (twisting) to prevent a sudden shutdown, which is standard behavior for lithium-ion batteries.
Check the status of the battery through the engineering menu or special applications diagnostics. If the wear exceeds 20-25%, replacing the battery can not only extend the life, but also remove the micro-lag associated with voltage drawdowns.
In some cases, the problem may be in the outgoing plume of the display or power controller, especially if the phone falls, but this is already in the field of hardware repair.