Re: gptzfsboot grew a lot after skein support was added; need knob to control bloat

On Sat, Jan 28, 2017 at 11:22 AM, Ngie Cooper <yaneurabeya_at_gmail.com> wrote:
>> What created a partition that small?
>
> Me.
>
> gpart up until last summer said that users should create 44kB
> freebsd-boot partitions -- des_at_ corrected that in r303289:
>
> -This example uses 88 blocks (44 kB) so the next partition will be
> -aligned on a 64 kB boundary without the need to specify an explicit
> -offset or alignment.
> -The boot partition itself is aligned on a 4 kB boundary.
> +We create a 472-block (236 kB) boot partition at offset 40, which is
> +the size of the partition table (34 blocks or 17 kB) rounded up to the
> +nearest 4 kB boundary.
>  .Bd -literal -offset indent
> -/sbin/gpart add -b 40 -s 88 -t freebsd-boot ada0
> +/sbin/gpart add -b 40 -s 472 -t freebsd-boot ada0

After some creative hacking... tada!

# find /usr/obj/usr/src/sys/boot/ -type f -name \*zfsboot -exec ls -l {} \;
-rw-r--r--  1 root  wheel  131584 Jan 28 12:07
/usr/obj/usr/src/sys/boot/i386/zfsboot/zfsboot
-rw-r--r--  1 root  wheel  47527 Jan 28 12:07
/usr/obj/usr/src/sys/boot/i386/gptzfsboot/gptzfsboot

-- wait, why is the size of zfsboot vs gptzfsboot so different? Oh,
r304321 added that as `BOOT2SIZE`. Still, it seems a bit silly to only
increase the size of one bootloader and not the other 4 instances of
the bootloader :/. I don't understand the point in the size
restriction 100%, but I'll leave it be.

Patch will be available sometime next week if my testing goes well.

Cheers,
-Ngie