Increase Virtual CPUs from 1 to 2, 3 or 4?

Due to Whonix-Workstation 14 - increase default RAM? I have been experimenting with zram.

Problem is, with 1 CPU core only (current VirtualBox default), when RAM is full, VM CPU gets 100% used, feels like locking up (would take ages) and makes the system unusable. That while the host CPU is still underused. So that does not help too much.

Should we increase VirtualBox (and KVM…) virtual CPUs from 1 to 4 or so? Any reason against it?

Whonix 14 download version requires 64 bit hosts anyhow. How many CPU cores do most 64 bit hosts nowadays have anyhow?

What if we set VirtualBox virtual CPUs in ova settings by default to 4 but the host system only has 2 CPUs? Will VirtualBox automatically fix it (reduce virtual CPUs) or just show some error message?

Does someone have two cores only? Can anyone test that?

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In the case of Whonix KVM 1 CPU per machine seems to cut it even for video playback. I pin 1 cpu per vm to avoid machines co-sharing a CPU cache - as extra hardening against sidechannel attacks on crypto libraries. I’d like to keep that if I can.

Overcommitting cpu will cause the host to lock up if the user runs more than 2 GW-WS pairs from experience.

Quadcore is pretty standard now.

Try playing around with the zram settings, compression algo choices to find a better trade off for CPU use vs memory savings. My other suggestion is to try zswap which might be more easy going on CPU since older memory pages can be swapped out unlike zram.


No worries. No need to make this uniform among VirtualBox / KVM. Not going to push this on KVM. This of course stays up to the KVM maintainer (@HulaHoop) to decide.

Same for VirtualBox however for this discussion the context of “did you try when zram was active” is crucial. Then 1 vs 4 cores might make the difference between “practically frozen” (while theoretically you maybe wait ages for the lock up to end) and “still usable system”.

Yes, more work to do on that front. Complex subject.


No such issue. 5 CPUs would be an invalid setting on my system using VirtualBox gui settings. vboxmanage modifyvm --cpus 8 doesn’t cause a VM startup problem.

(Whonix is based on Kicksecure.)

The current implementation is stable. Switching to something like zram / zswap would require lots of testing on different systems. Currently not a priority. (About priorities.) Help welcome.