RAM usage

[Kevin Yan]

Hi peeps, I would like to seek your advise on the RAM usage of my MacBook Pro (2019).
I recently bought one, but only with a 8GB of RAM, I needed my RAM, thus, I changed it to a 16GB model.
I restore all my files and setting from my backup.

What is strange is, the number of apps opened and browser tabs opened are the same, but after checking the Activity Monitor on the Memory usage, it doesn't make sense.

Physical Memory: 16.00GB
Memory Used: 11.58GB
Cached Files: 4.12GB
Swap Used: 0 bytes

My question will be, how is it possible when my 1st Macbook Pro, which is with 8GB RAM able to support if the current memory used is 11.58GB??

 

[pau5]

You must only look at memory pressure. The Memory used is not true of actual use. You can research about how macOS manages ram.

 

[maflynn]

My question will be, how is it possible when my 1st Macbook Pro, which is with 8GB RAM able to support if the current memory used is 11.58GB??

I'm not sure I understand your question.

The ram statistics you listed show that you're using 11.58GB of ram, and the way macOS utilizes memory, that 11.58 is broken up by App, wired and compressed. That is the operating system is keeping 11.58 of data/applications in memory for usage and since the swap file is not being used, that means nothing is being written to the disk which is slower then ram.

For MacOS you can think of it, as free ram is wasted ram.

Looking at the ram pressure can be helpful as it tells you if the system thinks your usage is fine (green), a bit constrained (yellow) or its having issues (red).

 

[jerryk]

Computers use a virtual memory system. That means only parts of programs are in the real memory chips at any one time. So on a 8GN system you can have 4 programs that could use up to 8 GB (4 X 8 = 32 GB) each running at the same time, but each is only using 2 GB of real memory (4 X 2 = 8 GB) at this moment.

It is actually much more complex than this, but the bottom line is the amount of memory show in Activity Monitor is a snapshot of the memory the programs will/can use. And that usage changes from moment to moment based on available memory, program activity, user commands, etc.

Because of this complex relationship is hard to understand, Apple added the Memory Pressure graph to summarize. If it is green, adequate memory is available. If if goes to yellow or red, then you have memory issues. It is far from a perfect tool, but does summarize the conditions.

 

[revmacian]

macOS is based on BSD, which was based on Unix. I ran BSD on my computers for years and one of the first things I learned was that, in the BSD world, "unused RAM is wasted RAM" - BSD will use RAM whether it actually needs it or not.

Try not to worry too much about RAM. I have a 2017 MBP and a 2019 MBA, both base models, and I typically have 8 apps open with several tabs in Safari and my machines seem to do fine. Of course it depends on your workload, but don't worry about keeping a certain amount of RAM free.

 

[Kevin Yan]

I'm sorry that I wasn't clear with my description. Let me try again.

What I was trying to describe was:

• With the number of apps and browser tabs opened remain the same for both Macbook
• 1st Macbook has 8GB RAM
• 2nd Macbook has 16GB RAM
• Memory Used: 11.58GB
• Thus, in the first place, how did the 1st Macbook able to handle 11.58GB memory used when it only has 8GB RAM?

I hope the above is clearer.

I'm not sure I understand your question.

The ram statistics you listed show that you're using 11.58GB of ram, and the way macOS utilizes memory, that 11.58 is broken up by App, wired and compressed. That is the operating system is keeping 11.58 of data/applications in memory for usage and since the swap file is not being used, that means nothing is being written to the disk which is slower then ram.

For MacOS you can think of it, as free ram is wasted ram.

Looking at the ram pressure can be helpful as it tells you if the system thinks your usage is fine (green), a bit constrained (yellow) or its having issues (red).

 

[jeyf]

Let me try again.
What I was trying to describe was in the first place, how did the 1st Macbook able to handle 11.58GB memory used when it only has 8GB RAM?
I hope the above is clearer.

memory is virtual; if there is not enough RAM memory the OS uses the hard drive which is some what slower.

if your 1st MB met your computing needs i dont know why you must have the extra RAM

anyways enjoy it while you have it.?

 

[matram]

Memory Used: 11.58GB
Cached Files: 4.12GB

The 4.12 GB cached files, are files that are no longer used by your apps. The memory is available to other apps if they request it. But as long as no other apps request the memory the files are kept in memory, should you by any chance want to access them again. So in reality only 7.46GB are actually currently in use.

As other have said virtual memory management is somewhat complex, look at memory pressure and do not worry.

 

[jerryk]

I'm sorry that I wasn't clear with my description. Let me try again.

What I was trying to describe was:

• With the number of apps and browser tabs opened remain the same for both Macbook
• 1st Macbook has 8GB RAM
• 2nd Macbook has 16GB RAM
• Memory Used: 11.58GB
• Thus, in the first place, how did the 1st Macbook able to handle 11.58GB memory used when it only has 8GB RAM?

I hope the above is clearer.

You are confusing memory used and memory minimally required. Your browser does not need 11.58GB. It can get by on a tiny fraction of that memory. However at this moment there are no other demands for that memory. So the OS leaves the memory associated with your browser since the browser might want the data in that memory or reuse this memory for other data in the future. And de-allocating the memory from the browser process, and then reallocating it later to the process is much slower than just leaving the memory associated to the process.

BTW, if you have a 3rd Mac with 32 GB and the same processing load, that 3rd Macbook might show 15-16GB of memory used because the process at various times used additional memory.

This is why just taking a single snapshot (i.e. looking at Activity Monitor's memory tab once) of what memory is used is a terrible way to try to measure your actual memory needs. You need to look at memory and other associated statistics over time and see what the trend is. This is what the Memory Pressure graph does.

Bottom line, memory usage is dynamic, and grows and shrinks based on demands from all of the processes running on a system. All processes demand memory in real-time and it is up to the OS memory management to meet these demands.