Why are some program taking much more memory?

OS type and version UBUNTU 20.04
Virtualmin version 7.2-1

I am trying to monitor and optimize memory usage on different systems. On a newly installed server with 12G ram that doesn’t host any site yet, I see BIND is claiming 58MB of memory while on another 4G server, it only uses 6MB. Why is this difference?

If BIND is operating as a local caching name server, in addition to being authoritative, it can grow quite a bit. But, 58MB is still quite small. Some of it will be shared libs, some will likely be memory mapped disk cache and can be swapped out without delay (I don’t actually know the memory architecture of bind, but I’m pretty confident that’s how it works…I think everything goes to disk, including cached recursive lookups and memory holds on to it for speed).

Even if both are offering caching name service, one can still be bigger than the other, if it is more active (i.e. more local services are making more requests for outside lookups).

It could also be a sign of misconfiguration…if you’re allowing recursive lookups to anything other than localhost or your local networks, that would be a security concern. Virtualmin configures it for local recursive use only, but if you already had configuration to allow others to make recursive queries it wouldn’t have undone that, most likely (we re require a freshly installed OS, we don’t try to fix it when it’s not).

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