4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4104 ::spa_space no longer works
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Sebastien Roy <seb@delphix.com>

*** 12,22 ****
  .\" CDDL HEADER in each file and include the License file at
  .\" usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this
  .\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
  .\" own identifying information:
  .\" Portions Copyright [yyyy] [name of copyright owner]
! .TH ZPOOL-FEATURES 5 "Mar 16, 2012"
  .SH NAME
  zpool\-features \- ZFS pool feature descriptions
  .SH DESCRIPTION
  .sp
  .LP
--- 12,22 ----
  .\" CDDL HEADER in each file and include the License file at
  .\" usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this
  .\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
  .\" own identifying information:
  .\" Portions Copyright [yyyy] [name of copyright owner]
! .TH ZPOOL-FEATURES 5 "Aug 27, 2013"
  .SH NAME
  zpool\-features \- ZFS pool feature descriptions
  .SH DESCRIPTION
  .sp
  .LP
*** 227,237 ****
--- 227,256 ----
  pool (even before any data is written). Since this feature is not
  read-only compatible, this operation will render the pool unimportable
  on systems without support for the \fBlz4_compress\fR feature. At the
  moment, this operation cannot be reversed. Booting off of
  \fBlz4\fR-compressed root pools is supported.
+ .RE
  
+ .sp
+ .ne 2
+ .na
+ \fB\fBspacemap_histogram\fR\fR
+ .ad
+ .RS 4n
+ .TS
+ l l .
+ GUID    com.delphix:spacemap_histogram
+ READ\-ONLY COMPATIBLE   yes
+ DEPENDENCIES    none
+ .TE
+ 
+ This features allows ZFS to maintain more information about how free space
+ is organized within the pool. If this feature is \fBenabled\fR, ZFS will
+ set this feature to \fBactive\fR when a new space map object is created or
+ an existing space map is upgraded to the new format. Once the feature is
+ \fBactive\fR, it will remain in that state until the pool is destroyed.
  .RE
  
  .sp
  .ne 2
  .na