New iMac with M4

Re:New iMac with M4 by foldr on Monday October 28, 2024 @12:17PM (#41972820)

The OS will use more RAM if you give it more RAM. The fact that you are currently using 46GB on an (I assume) 64GB model doesn't necessarily mean that your workload would run badly on a 32GB or 16GB model.

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Re:New iMac with M4 by TheOtherHobbes on Monday October 28, 2024 @05:25PM (#41976498)

It's more likely to mean exactly that, because the less RAM, the more disk swapping.

At some point it becomes impossible for the OS to keep everything it wants in RAM at the same time, and then you get an orgy of disk thrashing and a potential lock-up.

This is not theoretical. I've had it happen on both Macs and Windows machines, sometimes with just a single main app running.

At best you'll get obvious delays if you switch apps, as pages get dumped to disk while other pages are loaded.

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Re:New iMac with M4 by foldr on Monday October 28, 2024 @05:50PM (#41976785)

Yes, you may get some swapping, but with a fast SSD that won't necessarily degrade performance too much.

Some RAM is used for file caching and other optional stuff, so not all of the additional usage will translate into swap if RAM is reduced.

MacOS also makes use of RAM compression, which increases the amount of memory pressure that can be sustained before swapping is necessary.

All in all, it's pretty complicated, and the only way to know if a workload will perform acceptably on a machine with less RAM is to try it.

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