ZFS perfomance regression in FreeBSD 12 APLHA3->ALPHA4

[Mark Johnston]

On Wed, Sep 05, 2018 at 05:04:56PM +0300, Subbsd wrote:
> Hi,
> 
> I'm seeing a huge loss in performance ZFS after upgrading FreeBSD 12
> to latest revision (r338466 the moment) and related to ARC.
> 
> I can not say which revision was before except that the newver.sh
> pointed to ALPHA3.

Could you please try reverting r338416 to see if that fixes the problem?

> Problems are observed if you try to limit ARC. In my case:
> 
> vfs.zfs.arc_max="128M"
> 
> I know that this is very small. However, for two years with this there
> were no problems.

Two years on -CURRENT?  How often did you update?