ci_heartbeat_uptime_cache
ci->ci_heartbeat_uptime_cache = time_uptime32;
atomic_store_relaxed(&curcpu()->ci_heartbeat_uptime_cache, uptime);
cache = atomic_load_relaxed(&curcpu()->ci_heartbeat_uptime_cache);
d = uptime - atomic_load_relaxed(&patient->ci_heartbeat_uptime_cache);
db_read_unsigned(&ci->ci_heartbeat_uptime_cache),