TDB lockall necessary? (was: non-representative DB benchmark)

[Matthias Andree]

Gyepi,

do we really need tdb_lockall? It's a massive performance hog, and
tdb_store for instance appears to lock the key it is about to modify.

> ** TDB 1.0.6:
> * load:
> 7.25user 0.62system 0:08.42elapsed 93%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (76032major+298minor)pagefaults 0swaps
>
> * add:
> 3.80user 0.23system 0:04.09elapsed 98%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (27111major+359minor)pagefaults 0swaps
>
> * score:
> 98.11user 0.56system 1:39.48elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (1040major+305minor)pagefaults 0swaps

This is TDB without tdb_lockall, adding is much faster -- although
reading is still awfully slow (tdb_fetch

* load:
7.19user 0.03system 0:10.41elapsed 69%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (924major+106minor)pagefaults 0swaps

* add:
0.69user 0.07system 0:01.09elapsed 69%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (462major+1105minor)pagefaults 0swaps

* score:
78.51user 0.79system 1:22.35elapsed 96%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (951major+305minor)pagefaults 0swaps

-- 
Matthias Andree

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