MFC r273267:

Add tunable vfs.zfs.space_map_blksz for space map's maximum block size.
MFC r273026:

Add a tunable for arc_shrink_shift (vfs.zfs.arc_shrink_shift) that
controls how much fraction, 1/2^arc_shrink_shift, should be reclaimed
when there is memory pressure.

Submitted by:	Richard Kojedzinszky <krichy at tvnetwork.hu>
MFC r272974,272976:

Add ${name}_env and ${name}_prepend.  ${name}_env is an argument list which
will be passed to env(1).  ${name}_prepend is simply prepended to the command
line for $command.
MFC 273644,273738:
Clarify that pthread_cleanup_push()/pop() are implemented as macros that
create a new code block and thus must be balanced at the same lexical
scope.  (This is also a requirement in POSIX.)

PR:		194280
Submitted by:	dr2867.business@pacbell.net
MFC 273834:
Rework the EXAMPLES section to be a bit clearer.
- Add an example of using etcupdate diff.
- Create a subsection on bootstrapping that is below the simple
  examples.  This should make it clearer that 'etcupdate extract' is
  a one-time operation and not part of the common workflow.  It also
  adds more suggestions on when bootstrapping is needed and additional
  steps to make future merges simpler.
MFC 273598 273602 273607 273613 273647:

    Userland HPET support.
MFC r273711:
Allocate buffer for READ BUFFER/WRITE BUFFER commands on demand.

These commands are rare, but consume additional 256KB RAM per LUN.
MFC r273730, r273731:
Reduce code duplication around Write Exclusive persistent reservation.

While there, allow some more commands to pass persistent reservation.
MFC r273809:
Implement better handling for ENOSPC error for both CTL and CAM.

This makes VMWare VAAI Thin Provisioning Stun primitive activate, pausing
the virtual machine, when backing storage (ZFS pool) is getting overflowed.
MFC: r272243

  Add missing library dependencies.
MFC: r272245

  Remove duplicate prog.
MFC r273737, 273739

Clarify the documentation of pmcstat:
the -d argument should be passed before -p, -s, -P or -S to be taken in account

Differential Revision:	https://reviews.freebsd.org/D1011
Reviewed by:	adrian, gnn
MFC: r272248

  - Cleanups pc98 code.
  - Remove unworked formats.
MFC r273727:
Original commit message was
Allow the vfs.nfsd knobs to be set from loader.conf (or using
kenv(8)).  This is useful when nfsd is loaded as module.

As I understand, automatic fetch from kenv does not work in stable/10.
Merge the change still, to reduce code difference.
MFC r273728:
Add a method to iicbus to request IIC_M_NOSTOP behaviour for multibyte
transfers to be default.
MFC: r272252

  Drop the 3rd clause from all 3 clause BSD licenses.
MFC: r272255

  Supress clang warning for FreeBSD printf %b and %D formats.
MFC: r272256

  Switch from lib/libstand to sys/boot/libstand32.
MFC: r272258
  - Cosmetic changes.
  - Reduce diffs against i386.

MFC: 272259
  MFi386: Enable QUOTA, PRINTF_BUFR_SIZE and puc.
MFC: r268475 (by imp)

  Make SERIAL support optional again. Enable it for i386 because a huge
  percentage of machines has a 16550. Disable it for pc98 since only a
  tiny fraction of them have one.