Yes, what Lei wants to say is the "memory fusion" hyped by mobile phone manufacturers.

When vivo introduced this technology for the first time at the press conference last year, it also made several pages of PPT to introduce it.

Through its own memory black technology, 3G is transferred from idle flash memory to running memory, and the running memory is changed from 12G to 15G.

Vivo also said that this can significantly improve the system's background keep-alive ability, and the mobile phone runs smoothly.

Do you think it is very profitable to see this function for the first time?

After all, I used to want to buy a mobile phone with larger memory, but I had to pay more for it myself.

Now with this technology, it is equivalent to the manufacturer giving away memory for nothing. Wouldn't it be economical and smooth to buy a mobile phone 6G in the future?

Under the leadership of vivo, several mobile phone manufacturers followed suit and released similar "memory fusion" functions.

OPPO, for example, even pulls the extensible running memory to 7GB.

OPPO indicated that 12G running memory of this machine has been expanded to be equivalent to 19GB running memory.

Huawei followed closely, and announced the memory expansion technology at the press conference.

On the contrary, Xiaomi kept a low profile in this respect and didn't publicize anything, so he added the function of "memory expansion" in the latest beta version of MIUI 12.5.

However, for the sake of performance, only Snapdragon 865, 870 and 888 flagship or sub-flagship models can be used at present.

Moreover, compared with other mobile phone manufacturers, MIUI is obviously more conservative, and only does 3G storage expansion at most.

Then the question is, is the "memory expansion" promoted by manufacturers useful?

It is certainly useful for Xiao Lei to draw a conclusion from the beginning, but it is far less exaggerated than those PPT.

Even if you add 20GB of extended memory to your mobile phone, it can't be the same as native running memory, and the two can't be simply promoted.

What is 12+8=20GB? Obviously, gimmicks outweigh practicality.

Before talking about the "memory expansion" of mobile phone manufacturers, we have to start with the virtual memory of computers.

I believe everyone is familiar with this interface, which is the virtual memory setting of Windows system.

This function has been on PC for a long time, and it is turned on by default.

When the computer memory (RAM) is insufficient, the system will temporarily store some processes to the disk to prevent the software from crashing or flashing back.

However, the reading and writing speed of the disk (ROM) is definitely not as fast as that of the memory, and frequent reading and writing will cause the computer to get stuck.

In this case, we can't say that adding 10GB virtual memory to a computer with 4G memory will result in 14GB memory, right?

In the Linux kernel, there is a similar virtual memory mechanism, but the implementation method is not the same as Windows.

Taking Android as an example, the most common methods to alleviate running memory shortage are Zram and SWAP.

In most cases, mobile phone manufacturers will not open the SWAP of mobile phones as virtual memory.

Because this function really hurts the flash memory (ROM) of the mobile phone, it is also easy to cause the mobile phone to get stuck.

Especially in the emmc era, SWAP will seriously affect the performance of mobile phones because of the slow reading and writing speed of mobile phone flash memory.

As for why the side effects are so great, we should continue to look down and know.

To put it bluntly, SWAP is to take a small area from the flash memory of the mobile phone and use it as memory.

When the running memory of the mobile phone is really insufficient, put the temporarily unavailable processes into the exchange partition to alleviate the running memory shortage.

When the running memory is enough, the process temporarily stored in the swap partition will be brought back to the flash memory.

This will be a great test of the flash memory reading and writing speed of the mobile phone.

If the flash memory reads and writes too slowly, it will cause serious blocking when we need to put the exchanged data back into the memory.

Moreover, frequent reading and writing will greatly shorten the life of flash memory, which could have been used for 10 years, but it may be broken in three years. ...

Considering that SWAP has damaged the life of flash memory and poor performance, Android introduced a new memory expansion technology-ZRAM in version 4.4.

The principle of Zram is similar to SWAP, which divides a part of mobile phone memory for data exchange.

When the memory of the mobile phone is insufficient, the inactive processes are compressed and temporarily stored in the Zram area, thus increasing the available memory in disguise.

When the memory of the mobile phone is enough, decompress the process data that needs to be used.

Maybe everyone will be a little confused. For example.

For example, Xiao Lei ran a large software, put it in the background, and found that it actually occupied 2G of running memory.

At this time, if the Zram of the system is active enough, it will automatically compress and package idle processes.

After Zram compression, the memory that originally occupied 2GB only occupied about 6 14MB, which was equivalent to freeing up 1434MB for the system.

As for the compression ratio, it will generally be around 20~45%, depending on the compression algorithm and system performance.

Compared with SWAP, Zram has obvious advantages, because it originally separated an area from memory to process compressed data.

The data exchange from memory to memory will be much faster than that from memory to flash memory, and the exchange efficiency will be higher without hurting flash memory.

At present, it has become a routine means for major mobile phone manufacturers to make the background alive.

However, Xiao Lei has to say, however, Zram also has shortcomings.

When compressing and decompressing memory data, CPU resources are consumed.

The more active the Zram call, the greater the CPU load.

If everyone uses the flagship processor, it can be said that if you buy a Snapdragon 662 mobile phone, Zram is simply a CPU killer, causing the phone to get stuck.

Considering the obvious advantages and disadvantages of the two virtual memory technologies, the "memory fusion" of mobile phone manufacturers adopts a compromise scheme.

It is to combine Zram with SWAP, and when memory is tight, Zram is preferred to compress idle background data.

If Zram exceeds a certain threshold, a small amount of data is transferred to the flash memory.

MIUI development also explains this function, focusing on the fact that extended memory is not exactly the same as ordinary memory.

Since it is not a new technology, why have mobile phone manufacturers started to expand their memory recently?

A very important reason is that because of the progress of flash memory technology, the processors of flagship mobile phones are now relatively strong, and the flash memory is basically UFS 3.x, so the reading and writing speed is guaranteed.

In addition, the optimization of resource allocation at the bottom of Android is relatively mature.

While improving the mobile phone experience, manufacturers can take the opportunity to market a wave. Why not?

But marketing belongs to marketing, and equating this virtual memory with physical memory is suspected of deceiving consumers. ...

Moreover, the background management mechanism of the system itself is more complicated, which does not mean that opening 8G extended memory can guarantee not to kill the background.

Finally, to make a small summary, if everyone's mobile phones have more than 12GB of memory, then there is no need to open memory expansion, and Zram enabled by default is enough.

Remind everyone, really don't buy a mobile phone on the "memory integration" boasted by the manufacturer. When you get it, it's too late to find that it's not as smooth as you thought.