Comment 32 for bug 1838575

As outlined in the past conceptually there is nothing that qemu can do.
The kernel can in theory get memory zeroing to become concurrent and thereby scale with CPUs but that is an effort that was already started twice and didn't get into the kernel yet.

Workarounds are known to shrink that size massively (HP).

Also this is nothing the kernel Team would usually "do" they would follow upstream on it, so I'm leaving it open but low for them.
I realized those discussions where going on but not linked here.
=> https://<email address hidden>/T/
=> https://lwn.net/Articles/728023/
=> https://blogs.oracle.com/linux/making-kernel-tasks-faster-with-ktask,-an-update

Is one example. I'd ask the kernel Team to keep an eye open for that, be encouraging in discussions. This really has a huge benefit in those use cases.