RAM usage

[ProQuiz]

I had 16 GB RAM in my MacBook Pro 14" (M2 Pro). With just 3 or so tabs open in Safari and some light apps like Mail and Discord, RAM usage was around 10 GB. Is this right? However, while the RAM usage was around 10 GB, the Memory Pressure graph was still very low and in the green zone. On my Windows 10 desktop PC with 16 GB RAM, I have to open MANY apps to get it to go up to 10 GB RAM usage.

Also, on my MacBook, after a fresh boot, RAM usage would be around 5 GB with nothing open. On my Windows 10 PC, after a fresh boot, RAM usage is around 2.8-3 GB. After I open my daily apps and start running them in the background (like Steam, Discord, etc.), RAM usage settles at around 5 GB (which is the same amount as macOS after a fresh boot and nothing open).

Does macOS handle RAM differently than Windows or is Windows just "lighter" on RAM than macOS?

 

[gilby101]

You use the phrase "RAM usage". That really is too imprecise. With a 16GB MBP, all RAM will be used.

How did you measure "RAM Usage"?

macOS memory management is based on that of Unix which goes back ~50 years. Windows memory management grew from that on VAX/VMS - 46 years. The two are somewhat different and measures for one do not easily translate into the other - except that both try to make best use of memory. In that view both "use" all the RAM.

 

[thebart]

This matches with my observation. I think my Mac is using more memory mainly because it doesn't have a discrete GPU

 

[h9826790]

20 years ago, people tried to get as much free RAM as possible.

But now, we know that's not the correct way to utilise hardware. Idle RAM is useless.

Therefore, modern OS is designed to use free RAM as system cache to improve the overall performance.

e.g.

If your computer has 16GB RAM, and only use 2GB, but leave 14GB free to the system. Is that a good sign? No, because there are 14GB of RAM doing nothing but just sits there.

So, how about on top of the mandatory that 2GB usage, we utilise the RAM to store another 3GB of frequent use data. So that when the CPU want to access those data, they are already in the RAM, no need to wait for the storage device to response. Also, no need to re-read them again and again from the storage device.

Is this better now? Yes.

Apart from initially take some time to load the data into RAM. The system overall runs faster. And use less power (because less "read from storage" is required).

So, as long as there are free RAM, we can load more data into the RAM to speed up the system. Ideally, keeping the RAM usage at 99% is the best. However, this will create another problem. Because when a user want to open a new program, there has to be some free RAM. If the RAM usage is already at 99%, even most of the data can be moved, but it still takes CPU cycles, time, and power to create free RAM.

Therefore, modern OS memory management use many different kind of algorithm to decide which data should stay inside the RAM, and how much free RAM the system should reserve for the users.

Both Windows and macOS has this kind of algorithm, but they do it differently, and also present the info to the user in a different way.

For macOS, in general, as long as the memory pressure is green, you don't need to worry about the RAM usage. The OS sometimes may even choose to use SWAP but keeping some frequent use data inside the RAM. As an end user, we don't need to touch it. Just let it does its own job. Then most likely everything will be fine.

Of course, in the case of Apple Silicon, because the GPU also share use the unified memory. Therefore, it's so easy to use few more GB if you compare to a Windows computer (even the Windows PC only has iGPU, but so far, no PC iGPU like the Apple Silicon that can utilise all unified memory as VRAM (modern browser use VRAM to accelerate). Therefore, you won't see the same RAM usage in Windows.

 

[Howard2k]

You want it to use the RAM since it's far faster than SSD and far, far, far, faster than swapping to HDD. If it needs to use the memory then it will do so, and it will release/swap over time as needed.

Of course, it's been 20 days since I last rebooted, and I'm on Ventura 13.6, the most up to date version of Ventura, and Macrumors in Safari is claiming 2.18GB of RAM. But a reboot and it will force it to be released.

But again, you want it to use RAM if it feels the need to do so.