Slow OS image build for arm64 image on amd64 host

[lueschem]

Using Debian trixie the OS image build became pretty slow when executed on an amd64 host. Especially the Python interpreter startup was observed to be very slow:

On bookworm:

root@d6c3243fd469:/# time python3 -c "print('hello')"   
hello

real    0m0.343s
user    0m0.328s
sys 0m0.017s

On trixie:

root@cf115e77533a:/# time python3 -c "print('hello')"
hello

real    0m1.213s
user    0m1.203s
sys 0m0.012s

It looks like a significant speedup can be achieved by setting the QEMU_CPU environment variable:

buildah config --env QEMU_CPU=cortex-a57 edi-d35b0e3a-429715a5

The interpreter startup will now be more than 3 times faster:

root@cf115e77533a:/# time python3 -c "print('hello')"
hello

real    0m0.339s
user    0m0.330s
sys 0m0.012s

[lueschem]

The QEMU_CPU environment variable is "hidden" when Ansible is using the sudo command:

root@cf115e77533a:/# env | grep QEMU
QEMU_CPU=cortex-a57
root@cf115e77533a:/# sudo env | grep QEMU