changing space map blksz, commit from illumos

[Matthew Ahrens]

Xin pointed out that this change is in head.  The problem is that I was
looking at release/10.1.0.  Looks like it's already in releng/10.2 so
that's great, sorry for the noise!

--matt

On Wed, Sep 16, 2015 at 6:09 PM, Matthew Ahrens <mahrens at delphix.com> wrote:

> I would like to change the space map block size on FreeBSD, to improve
> performance on a system with very large vdevs.  This was made possible in
> illumos (exactly!) a year ago by the commit below.  Does anyone know if
> there's a technical reason that this was not ported to FreeBSD?  If not, it
> would be great if someone wants to pick it up, otherwise I'll try to do so
> when I have time.
>
> commit b1be2892dd07cf9a97d47ad06334cdc879196aaf
> Author: Matthew Ahrens <mahrens at delphix.com>
> Date:   Tue Sep 16 11:53:58 2014 -0800
>
>     5164 space_map_max_blksz causes panic, does not work
>     5165 zdb fails assertion when run on pool with recently-enabled
> spacemap_histogram feature
>     Reviewed by: Christopher Siden <christopher.siden at delphix.com>
>     Reviewed by: George Wilson <george.wilson at delphix.com>
>     Reviewed by: Saso Kiselkov <skiselkov.ml at gmail.com>
>     Approved by: Dan McDonald <danmcd at omniti.com>
>
> --matt
>