Re: adding swap when expanding root filesystem

Hi Mike,

On Mon, Nov 07, 2022 at 10:10:38AM -0600, Mike Karels wrote:
> This question is not really arm-specific, but I couldn't think of a better
> mailing list for it.
> 
> There are peridic issues reported on small systems like Raspberry Pi
> where people are running buildworld or poudriere and running out of
> memory.  As the user gets no control over the disk layout when installing,
> there is no option to add swap space on the install image.  I have added
> swap space on a USB disk, but this is often not an option.  It occurred
> to me that it might be reasonable to add swap space before expanding
> the root filesystem if there is sufficient space.  I have a prototype,
> and wondered if this is a good thing to do.  Granted, this will often
> create swap on microSD, which is not optimal, but probably better than
> nothing.
> 
> The current prototype creates a swap partition which is 1/10 of the disk
> if the disk is at least 15 GB and the initial root partition is no more
> than 1/3 of the disk, but only up to 1.5x of physical memory.  I would
> probably enable this by default, but provide a way to disable it via a
> kenv variable and/or a variable in /etc/rc.conf.
> 
> Thoughts?
> 
> 		Mike

That would be very welcomed addition. I personally ofter run into problems
when I try get a crash dump from my RPi4, since no dumpdev can be set
without a separate swap partion. An USB stick worked for I while, but it
just went dead at some point.

And the genet(4) driver doesn't support netdump(4).

--Gordon