64GB ram usage

[jqc]

I just got a new MacBook Pro 14 M1 (64GB RAM, 2TB storage, Max chip) from B&H for an insane $2300. I am coming from a 2020 M1 13" MBP 8GB RAM 56GB storage.

My main use case is work, so lots of outlook, multiple word, excel, ppt docs, Sharepoint through onedrive, many safari tabs. I was constantly in the yellow for memory pressure with multiple GB swap but never noticed a slow down in performance.

With the new MBP 64GB, of course no swap but I am very surprised how much memory is used, about 21GB for applications. AS Long as there's no swap I don't care but found it interesting. Do apps use more RAM with 64GB simply because it's available? I don't think my old 8GB RAM used that much RAM with swap with similar usage.

See attached screen shot.

As aside, the other big difference besides the obvious upgrades is that the 14" runs a lot hotter, hovering around 45-48C with "normal usage", going to ~75C with Teams video call and screen share, case warm to hot. My 13" case was cool to the touch, around 27C with normal usage, occasionally getting to ~50C. This is what I miss most about the 13"

 

[ArkSingularity]

Yes, MacOS will use more RAM if it is available. It's expected behavior, macOS is caching things and making good use of memory as much as possible.

A lot of it comes from memory mapped IO pages (RAM used for storing the contents of binaries, parts of your application, or resources/files that may have been opened by you or a program). Much of this is fairly easy to purge, but MacOS will try to keep as many of these in RAM as possible to help speed up any future accesses to them in case they're needed again in the near future. If you have more RAM, MacOS will be slower to purge them, hence higher RAM usage.

Memory pressure is the better metric to look at. It gives you a much better idea in terms of how much headroom you actually (for all intents and purposes) have. If you're remaining in the green, you're nowhere near your system's limit.

 

[dmccloud]

Mac OS will use as much RAM as possible. However, as AS stated, memory pressure is the key metric to look at. Think of memory pressure like a tachometer on a car. If it goes into the red, you run the risk of problems. But if it's in the green, you're good to go.



Even if my MBP was currently using 28-30GB of RAM, I would have no reason to be concerned unless that memory pressure was in the yellow or red.

 

[jqc]

Mac OS will use as much RAM as possible. However, as AS stated, memory pressure is the key metric to look at. Think of memory pressure like a tachometer on a car. If it goes into the red, you run the risk of problems. But if it's in the green, you're good to go.

View attachment 2256780

Even if my MBP was currently using 28-30GB of RAM, I would have no reason to be concerned unless that memory pressure was in the yellow or red.

cool, and that small amount of green is all I am seeing. A refreshing change from the constant large bit of yellow on my 2020 M1 8GB MBP - but again stress, I never saw a slowdown in my 2020 MBP in my everyday tasks (no photo, video editing)

 

[Basic75]

Yes, MacOS will use more RAM if it is available. It's expected behavior, macOS is caching things and making good use of memory as much as possible.

That explains the 30GB of cached files, but not the 21GB of application memory mentioned by @jqc.

 

[ArkSingularity]

That explains the 30GB of cached files, but not the 21GB of application memory mentioned by @jqc.

Well, on MacOS, some of the memory listed as "in use" will consist of these kinds of purgeable pages also. MacOS handles this slightly differently than Windows or Linux might, and will generally purge the page cache much more slowly. This is done to take better advantage of compressed memory, as it turns out MacOS will simply compress some of these if it has the headroom to do so (this is a good thing, as it's much faster to decompress them from memory than it is to grab them fresh from disk in the event that they are needed again).

Modern demand paging kernels (Windows, Linux, MacOS, etc) won't actually load an entire binary or file just because it's been opened. When you open Chrome, for example, it's not loading all of the executable data for Chrome into RAM. It's pretending to (it maps these files into virtual memory so that the application can access any part of the binary as if it were in RAM), but the kernel determines which pages will actually be in RAM versus which ones will just be on the disk and be "mapped" to virtual memory. As you can imagine, this is important for making efficient usage of RAM, as the system could easily require 20GB+ just to boot your computer otherwise. However, these cached pages are still important. If you don't have a lot of room for your page cache (if you cannibalize it to the point of being nearly non-existent), the kernel will constantly be purging them and re-loading pages that it needs, which is just as bad for your general performance as swapping is.

MacOS is generally pretty smart about this and will sometimes compress some of these if it has the headroom to do so (as a result, some of the memory listed as "in use" may technically be purgeable also). This doesn't mean these pages are non-important, nor is they inconsequential to general performance. But the ballooning memory usage on higher RAM systems doesn't necessarily mean the system is anywhere close to being memory starved if the memory pressure is still low.

I did a test recently just to see how the MacOS sonoma beta would run on a VM with 2GB of RAM. It actually ran quite a lot better than I expected, only using 1.4GB of RAM at startup and 100-200MB of swap. Chrome ran fine as well (even with several tabs open and a handful of other apps in the background), although apps were noticeably slower to launch.