K 10
svn:author
V 6
rlibby
K 8
svn:date
V 27
2020-01-09T02:03:17.560530Z
K 7
svn:log
V 434
uma: unify layout paths and improve efficiency

Unify the keg layout selection paths (keg_small_init, keg_large_init,
keg_cachespread_init), and slightly improve memory efficiecy by:
 - using the padding of the final item to store the slab header,
 - not going OFFPAGE if we have a choice unless it improves efficiency.

Reviewed by:	jeff, markj
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D23048

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