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Memory pressure in iStats [MERGED]

rosegoldoli

rosegoldoli

macrumors 6502a
Original poster
Feb 21, 2019
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Hi All, I just got myself a new M4 iMac with 512GB / 10 / 10 / 24GB RAM.

I upgraded from the M1 iMac which I had the 512GB / 8 / 8 / 16GM RAM.

As you can see I opted for higher ram this time but I am curious if 32 GB RAM is better?

I see currently I am using 32-55% of memory pressure using iStats with just web browising, Spotify and Apple Music open (work reasons). Is this within normal range? I just don't wanna go overkill on RAM.

Thank you!
 
If it's in the green in activity monitor you're absolutely fine, even if it slips into yellow.

I have got a 64GB M2 and it's using, no, utilising 40GB for fairly light stuff. The more you have the more will get used, and be quickly available. I also bought with this ability as I keep my devices a very long time (13 yrs last MBP), likely 7 yrs for the current machine. So if programs are not well optimised or become more demanding in the future, I have a buffer of sorts and RAM is something you cannot offload as with external storage. That's the way I view this anyway.

What happens if you throw some heavy resources at it that you may plan to use? Just the trials of them, to see if the RAM doesn't then swap to disc?
 
Alpha Centauri said:
If it's in the green in activity monitor you're absolutely fine, even if it slips into yellow.

I have got a 64GB M2 and it's using, no, utilising 40GB for fairly light stuff. The more you have the more will get used, and be quickly available. I also bought with this ability as I keep my devices a very long time (13 yrs last MBP), likely 7 yrs for the current machine. So if programs are not well optimised or become more demanding in the future, I have a buffer of sorts and RAM is something you cannot offload as with external storage. That's the way I view this anyway.

What happens if you throw some heavy resources at it that you may plan to use? Just the trials of them, to see if the RAM doesn't then swap to disc?
Click to expand...
So I use adobe's web applications sometimes. When I used it the pressure went up to 56% and says the swap was 137 mB. These don't seem like extreme numbers, unless they are?
 
rosegoldoli said:
Hi All, I just got myself a new M4 iMac with 512GB / 10 / 10 / 24GB RAM.

I upgraded from the M1 iMac which I had the 512GB / 8 / 8 / 16GM RAM.

As you can see I opted for higher ram this time but I am curious if 32 GB RAM is better?

I see currently I am using 32-55% of memory pressure using iStats with just web browising, Spotify and Apple Music open (work reasons). Is this within normal range? I just don't wanna go overkill on RAM.

Thank you!
Click to expand...
IMHO, the more RAM, the better. I’ve come to consider 32 GB as the “base” RAM.
 
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I recently purchased an M4 Mac mini to replace my 2017 iMac. Both systems have 16 GB memory. On the iMac, memory pressure was always in the green. However, with the same set of apps open on the new Mac mini, memory pressure typically turns yellow.

On both the iMac and Mac mini, iStat Menu reports memory utilisation of around 70% to 80% with those apps open. However, memory pressure on the iMac stays around 35%; but on the Mac mini, it's usually around 50% to 60%.

I'm aware of the SoC architecture on the new Macs; but even with nothing open, memory pressure is higher on the Mac mini versus the iMac. Is it plausible that Apple changed the memory pressure algorithm on ASi systems? Not sure if at all relevant, but I have noticed that the x86 Mac appears to use swap a lot sooner than the ASi Mac, and the latter compresses a lot more memory.

I should also note that the iMac was running macOS 13, and this Mac mini is running macOS 15. I don't have "Apple Intelligence" enabled, and I did a Time Machine restore when I was setting up the new Mac. Given the unified architecture, I am aware that the Window Server uses the same unified memory to power the Apple Studio Display, but I don't think these factors reasonably explain the difference in memory pressure between the two systems.

Anyone else have any thoughts about this?
 
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rosegoldoli said:
So I use adobe's web applications sometimes. When I used it the pressure went up to 56% and says the swap was 137 mB. These don't seem like extreme numbers, unless they are?
Click to expand...
I don't really use Adobe products so cannot really compare. Right now I've got 16 active Safari windows open, many Apps open and I'm sitting at 5 % pressure (iStat). Exported in CaptureOne two Tiffs from RAW files and it was done almost before I pressed the export button. Pressure briefly jumped to 8% from 5%.

I don't know my way around configuration options on the M3/4, especially on the iMacs, but do recall having to get the Max to buy 64GB RAM.
Comparing metrics is quite difficult here. You said it went up to 56% but then settled again quickly? That it swapped at all with 24GB isn't terrific but the amount is nothing really.

So you have the option, return window still? Is 32GB possible without upgrading to a Max chip?
 
Is more RAM better? Yes.

Will it make a significant difference?

For most people just doing everyday things the answer is probably not. They'd just be giving more money to Apple.

Don't worry about the memory pressure color. It's highly misleading. There are plenty of people here pushing 8 and 16GB machines far harder than you are and it's working fine for them and no, your SSD isn't going to die because your memory pressure isn't green. That's a mostly unfounded fear.
 
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I guess 8GB is good enough for me.
MemoryPresure.jpg
 
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Ive been monitoring for a few days and it’s been at a 40-53% constant pressure. Nothings slowing down now but I just wonder if it’ll have long term effects. I want to keep this machine for at least 3.5 years
 
I also use iStatMenus but, if you open Activity Monitor, you can see a lot more active processes.
 
rosegoldoli said:
Ive been monitoring for a few days and it’s been at a 40-53% constant pressure. Nothings slowing down now but I just wonder if it’ll have long term effects. I want to keep this machine for at least 3.5 years
Click to expand...
There will be no "long-term effects". The machine is designed to swap out what's in RAM onto a file on the SSD when you're not working on it, and then swap it back in when you're working on it again. It's not going to destroy the SSD or anything else. You *might* notice a momentary pause when swap happens, but frankly that's less of an issue here in the fast SSD age than it was back when we were all booting off HDDs and it was a bigger performance hit.
 
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Just an update on my post:

It appears that the memory pressure goes down as soon as the system starts to swap.

I am reasonably certain that ARM Macs use memory compression more aggressively than x86 Macs for data that has not been used recently, and will only start to utilise the swapfile more aggressively when the memory pressure reaches a high threshold. This behaviour makes sense since the Apple SoC can compress and decompress data extremely efficiently.

I have consistently noticed that the memory pressure goes down to levels similar to my older x86 Mac as soon as the system begins to page-out data to the swapfile. Crucially, page-ins remain relatively flat for my workflow, which suggests that the system is (correctly) choosing to page-out the most infrequently used data, keeping more frequently used data within memory to maximise performance.

I also suspect the memory pressure settles with continued usage because the system can, over time, more accurately establish what data is being or likely to be frequently accessed, especially after processes have been running for an extended period of time. In my case, from a cold boot to launching all the apps and utilities that I need running, memory pressure can easily climb to 60%, but after many hours (with the same apps open), it's usually at 35% to 40%. Memory utilisation is probably a little higher overall, since there is no discrete GPU with its own memory – and also being two macOS versions newer that my old Mac – but not higher by an egregious amount.
 
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basdeninard said:
I am reasonably certain that ARM Macs use memory compression more aggressively than x86 Macs
Click to expand...
Apple's chips have a large amount of silicon dedicated to data compression, and they do seem to be perform more compression than Intel CPUs (and probably faster, too).
 
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Update: Think I've decided to return this iMac and go for the 32GB Ram model. I noticed from what I do I see the activity monitor go yellow and it's not like I am doing anything crazy (safari tabs open, imessage, phone mirroring etc). Not even my usual workload with adobe or using crossover/steam so that worries me because I want to keep this machine for at least 3 years.

If you guys think I am overthinking/worried about nothing that's also fair
 
rosegoldoli said:
Update: Think I've decided to return this iMac and go for the 32GB Ram model. I noticed from what I do I see the activity monitor go yellow and it's not like I am doing anything crazy (safari tabs open, imessage, phone mirroring etc). Not even my usual workload with adobe or using crossover/steam so that worries me because I want to keep this machine for at least 3 years.

If you guys think I am overthinking/worried about nothing that's also fair
Click to expand...
Am thinking that’s a reasonable move.
 
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