How fast is a macOS VM, and how small could it be?

>Starting with 4 virtual cores and 8 GB vRAM, where the VM ran perfectly briskly with around 5 GB of memory used, I stepped down to 3 cores and 6 GB, to discover that memory usage fell to 3.9 GB and everything worked well. With just 2 cores and 4 GB of memory only 3.1 GB of that was used, and the VM continued to handle those lightweight tasks normally.

Good reminder that there's a certain amount of memory tied up with each core (probably mainly page cache and concurrency handling etc).

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nasretdinov 11 minutes ago | parent | prev | next [-]

Honestly macOS probably can go much lower than that if you turn off some stuff that's not strictly necessary for a VM. The first iPhones only had 128 MiB of RAM and they ran a trimmed down version of macOS Tiger I believe. It's just that RAM has been quite abundant so far, so there was no real reason to try to trim it down, but it's definitely possible, and probably not that hard either, we just need to start trying again :)

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nottorp an hour ago | parent | prev | next [-]

> Starting with 4 virtual cores and 8 GB vRAM, where the VM ran perfectly briskly with around 5 GB of memory used

But... if you start applications inside your VM it will want the full 8 Gb you've allocated not the 5 Gb it uses at startup?

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stingraycharles 43 minutes ago | parent [-]

I don’t assume that macOS virtualization is advanced enough to support memory ballooning, or is that not what you’re referring to?

Edit: I stand corrected!

	▲	pyth0 31 minutes ago \| parent \| next [-]
		I don't assume anything either, but a single Google search is enough to dispel that [1] [1] https://developer.apple.com/documentation/virtualization/vzv...
	▲	sgt 20 minutes ago \| parent \| prev \| next [-]
		macOS is generally pretty amazing at efficient memory usage and VM handling. So even a 8GB machine can run pretty impressive workloads without having the user think the machine is underpowered.
	▲	nottorp 32 minutes ago \| parent \| prev [-]
		What will that help with if the host and guest combined need > physical ram?

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dieulot an hour ago | parent | prev [-]

I'm wondering if the Xcode simulator (without Xcode running) performs as well, my 2020 Intel MacBook Air has been incapable of running Safari in iOS smoothly for nearly all its life.