Looks good (not run tested).

FYI, I added this to src.conf:

grep LOADER /etc/src.conf

LOADER_GZIP_SUPPORT=no
LOADER_BZIP2_SUPPORT=no
LOADER_BIOS_TEXTONLY=no
LOADER_NFS_SUPPORT=no
LOADER_TFTP_SUPPORT=no
LOADER_CD9660_SUPPORT=no

While I agree with the rationale and the change:

In D40972#1062704, @arrowd wrote:

I just bumped into this and I wonder what's the rationale to perform promotion during bectl activate.
I want to keep the BE snapshot I'm creating a new BE from, but activating new BE removes the snapshot (well, transfers it to the new BE's dataset).

Addendum - @netchild has been running -CURRENT with this patch series for some time with no issues encountered so far.
@netchild please correct me if I've misunderstood something, but the machine in question is a laptop with 8GB of RAM and it is primarily used to run various jailed services (~30 jails) and build packages.

In my work for the automatic service jails (committed last week), I stumbled upon cases (in the base system) where some kind of functions were used to setup variables before starting the actual service, which was not necessary. When the automatic service jail is enabled for such a service, some of this stuff was run outside the service jail and didn't had the desired effect. After changing those scripts to not setup variables like that, it worked.

Address the last big comment from @fernape .

Fix issues outlined in the reviews (links are ok now, lists are rendered correctly, ...) and some minor change in phrasing.

This doesn't apply to -current anymore, mainly in vm_page.h (all used upto 0x8000). I tried a naive / mechanical implementation without researching/understanding this part, by using 0x10000 for VM_ALLOC_NOFREE, and with VM_ALLOC_COUNT_MASK set to 0x1ffff, and VM_ALLOC_COUNT_SHIFT set to 17, but this panics.

In D40772#969417, @mjg wrote:

If you can rebase both changes and show me how to collect fragmentation stats I can test this against a full ports tree build.

The summary tells the value ranges from 0 to 1. The reality is that it ranges from INT_MIN to 1000.

@alc you asked about a way to measure the fragmentation, is https://reviews.freebsd.org/D40575 maybe something which helps for this?