Comment 18 for bug 1830502

The biggest problem is that it isn't easily disabled because it is hardcoded in the script instead of being in /etc/apparmor/parser.conf.
Instead of hardcoding, it would had been better to just update that conffile and let dpkg update it if the user didn't change it (which is highly likely) or on new installs.

In /lib/apparmor/functions we have this:
# LP: #1383858 - expr tree simplification is too slow for some
# policy on 32bit ARM, so disable it for now
cache_extra_args=
if [ -d "$PROFILES_CACHE_VAR" ] && [ "$pdir" = "$PROFILES_VAR" ]; then
    cache_extra_args="-O no-expr-simplify"
fi

So now for machines with 2Gib of RAM and Snaps, Ubuntu 18.04 has become unusable.
I know the minimum requirements are 4Gib but it did actually work fine with 2Gib before so it is a bit sad to loose that capability.

My suggestion is to just revert that change and do it in parser.conf instead, so at least we have the option to easily modify it to retain some 2Gib support.

Thanks a lot for considering this!!!