Comment 4 for bug 2025030

I did a quick experiment in our "interfaces-many-snap-provided" test to see what impact the options have. I ran spread with:

$ spread -shell-after -v qemu:ubuntu-22.04-64:tests/main/interfaces-many-snap-provided

And inside spread (on 22.04) compiled the profiles with/without no-expr-simplify:

With "no-expr-simplify"
# /usr/bin/time -f '%E real, %M max-mem' apparmor_parser -O no-expr-simplify -S /var/lib/snapd/apparmor/profiles/snap.{test-snapd-policy-app-consumer,test-snapd-policy-app-provider-classic}.* >/dev/null
0:22.07 real, 22908 max-mem

Without "no-expr-simplify"
# /usr/bin/time -f '%E real, %M max-mem' apparmor_parser -S /var/lib/snapd/apparmor/profiles/snap.{test-snapd-policy-app-consumer,test-snapd-policy-app-provider-classic}.* >/dev/null
0:49.45 real, 13720 max-mem

Which seems to indicate that there is a trade-off here and moving away from "no-expr-simplify" will make the installs/refreshes slower but also reduces memory usage. It also seems like our normal tests do not catch the memory explosion that we saw here.