i had same question, and i have also x86 router with 4gb ram, it look like some caching, don't worry it is not an issue for linux based system
Too much memory cached - Installing and Using OpenWrt - OpenWrt Forum
i had same question, and i have also x86 router with 4gb ram, it look like some caching, don't worry it is not an issue for linux based system
Too much memory cached - Installing and Using OpenWrt - OpenWrt Forum