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

[Michal Nowak]

On 02/09/2021 13:29, Mark Tinka wrote:
> 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.

Mark, what's the exact BIND 9.16 version which is crashing for you? Why 
do you say that the reason for crashing is BIND running out of swap? How 
did you found out?

Note that BIND 9.16.19 was tripping over a misplaced assert, see 
https://downloads.isc.org/isc/bind9/9.16.20/doc/arm/html/notes.html#notes-for-bind-9-16-20.

Michal