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Date:      Mon, 10 Sep 2018 09:02:08 +0000
From:      "Thomas Mueller" <mueller6722@twc.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: swap config
References:  <10538979.gLySxXtyIk@chameleon.friedrich.org> <goQ6cy3nzG0mwIpbkUqxh1oUx_fBt0-pu1Q0e5cDUXJ6bqU78vCkuT6vak620ohxdpOtwEgleHeRChJpC6_iLHPyfWP686gV8AMUaC8islU=@protonmail.ch> <Ft-rBYuwEG1UY7W3ryi-9xyLUkJ-kWvDx5YZcA8nLPqT43G-zQDnwYgstFaHx0NHBU-_3ItMNzjvTHbPfoRs0M3bfc4gUN-VoxI1oxi4KPQ=@protonmail.ch> <20180910005743.3bf5df59@gumby.homeunix.com>

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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




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