[OSM-dev] Slow Osmosis

[Brett Henderson]

Andreas Kalsch wrote:
> Osmosis is very slow on my server.
> There is this option --write-null (--wn) which can be useful just to 
> check integrity of data. So I think Osmosis does everytime check it and 
> this could be a bottleneck because it has to cache some data in memory.
> Can this be the origin for being slow (next to my server) ?
>   
Can you give me some more info?  What command are you running?

If you're reading from a bzip file it will be slow with osmosis 
consuming large amounts of CPU, gzip files are far faster because they 
use native code.
If you're importing into a database the database itself is usually the 
bottleneck.

The --write-null task doesn't do *anything*, it simply discards all data 
passed to it.  There is no data cached in memory in that scenario.