swap config

[Thomas Mueller]

On Sun, 09 Sep 2018 12:40:03 +0000
Lorenzo Salvadore via freebsd-questions wrote:
        
> > My system has 16GB of memory, so I multiplied that by 4 to get 64GB.
> > I created a swap partition of 64GB.
> > When I boot, I get:
> > warning: total configured swap (16777216 pages) exceeds maximum
> > recommended amount (986928 pages).
> > warning: increase kern.maxswzone or reduce amount of swap.
> > I tried adding kern.maxswzone to /boot/loader.conf but it complains
> > no matter what value I set.
> > What should I do? I'm not actually swapping, since I have so much
> > memory, so I could turn swap off and re-create the swap partition.
> > Correct?

RW via freebsd-questions responded:

> IIRC there is a hard limit of 4XRAM, and there is an area of the
> partition reserved for metadata. I don't recall how the arithmetic is
> done, but it may be necessary to make kern.maxswzone a bit smaller than
> the number of 4kB pages in 64GB , and/or make the actual partition a bit
> smaller than the size implied by kern.maxswzone.

Are you sure?  What about an old system with 256 or 512 MB RAM that would need swap > 4 * RAM?

64 GB seems like overkill for 16 GB RAM.

Tom