ZFS arc sizing (maybe related to kern/145229)

[Rich]

A datapoint for you:
Now running 8-STABLE (plus the mbuf leak fix which went in recently),
here's my ARC stats and ARC sysctl settings after the server was up
for about a week (5 days) after that:
ARC Size:
        Current Size:                           587.49M (arcsize)
        Target Size: (Adaptive)                 587.63M (c)
        Min Size (Hard Limit):                  512.00M (arc_min)
        Max Size (Hard Limit):                  3072.00M (arc_max)

ARC Size Breakdown:
        Recently Used Cache Size:       98.28%  577.50M (p)
        Frequently Used Cache Size:     1.72%   10.12M (c-p)

ARC Efficiency:
        Cache Access Total:                     2602789964
        Cache Hit Ratio:                96.11%  2501461882
        Cache Miss Ratio:               3.89%   101328082
        Actual Hit Ratio:               87.65%  2281380527

and

        vfs.zfs.arc_meta_limit=1073741824
        vfs.zfs.arc_meta_used=548265792
        vfs.zfs.arc_min=536870912
        vfs.zfs.arc_max=3221225472

So it very clearly limits to near the minimum size, but whether this
is design or accidental behavior, I'm unsure.