[Tile-serving] [osm2pgsql] Reduce memory usage of node cache (#360)

[Paul Norman]

So, 
```
node cache: stored: 1484575472(54.67%), storage efficiency: 94.39% (dense blocks: 1406958, sparse nodes: 66070009), hit rate: -114.50%

Osm2pgsql took 31555s overall
```

So, the hit rate is marginally different, but this branch is 6% slower.

Looking in more details, 

```
                #360   master
processing n     820      809
processing w    6110     5766
processing r   11284    10568
pending ways    8125     7419
indexes         7083     6907
total          33536    31555
```

Processing node differences are within normal variations.

Because I ran both with `time` I have those numbers too

#360
```
52134.89user 3594.71system 9:18:56elapsed 166%CPU (0avgtext+0avgdata 16419744maxresident)k
294242648inputs+913034600outputs (56448major+4575021minor)pagefaults 0swaps
```

master
```
47005.27user 2260.20system 8:45:55elapsed 156%CPU (0avgtext+0avgdata 16459960maxresident)k
324145584inputs+52018888outputs (28397major+1744337minor)pagefaults 0swaps
```


---
Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/osm2pgsql/pull/360#issuecomment-117047433
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tile-serving/attachments/20150630/dae6c5ed/attachment.html>