BIND 'max-cache-size' Value on FreeBSD-13.0

[Mark Tinka]

Hi all.

Ever since we moved from BIND-9.11 to BIND-9.16, we've been experiencing 
'named' crashing after 24hrs - 36hrs on high-load resolver-only servers, 
running on FreeBSD-13.0.

We found that the reason for this was due to BIND running out of swap space.

An increase in swap space by creating a 4GB swap file did not help.

So we are now playing with the 'max-cache-size' value in BIND. The 
system has 15GB of physical RAM. Limiting BIND to 13GB of memory does 
not work; 'named' still crashes due to a lack of swap space.

We have then switched to % values, and it's still crashing for the same 
reason at 90% and now 80%.

We are now testing 70%.

Anyone have some idea of how we can get this under control?

Is there a possibility that BIND is not properly understanding how much 
physical RAM is available to FreeBSD, and just burns through it anyway, 
tripping swap space in the process? I can't think of any reason why BIND 
would keep burning RAM if it has been told to limit its demand to a 
certain value or %.

All help appreciated. Thanks.

Mark.