[OSM-dev] mapnik rendering very long on low zoom

[sly (sylvain letuffe)]

Hi,

For different reasons, I need re-building a whole lot of rather old (~8month) 
mapnik tiles across europe I had.

I am in the process of building it from zoom 0 to zoom 12 (other levels are 
handeled with on demand cache system )

From level 0 to 5 things are going quite fast (presumably because there is 
almost nothing on it) but zooms ~6 to 8 are generated terribly slowly.
9 to 12 being still quite slow and 13 or less starts to be manageable.

I'm using the generate_tiles.py program and a one year old mapnik file to 
trouble shoot the problem (the same I used 8 month ago) and I can't remember 
this process to be that slow !

The machine seams io-bound, 
top : 
Cpu(s):  4.8%us,  1.8%sy,  0.0%ni, 69.4%id, 24.0%wa,  0.0%hi,  0.0%si,  0.0%st
load 1.00, 
iostats tels me the reading speed on disks is around 2MB/s (~100 times less 
than my burst disk/raid0 speed)
swap isn't used

I've tweaked postgres with the wiki recommanded settings
and a command like this :
$ time ./nik2img.py -m osm_copy.xml -i jpeg -o test.jpeg -s 500,500 -e 
2,40,8,46
(...)
real    5m24.251s
user    0m5.684s
sys     0m0.572s

poorly generates a small image in 5 minutes !
(dual core 2.6GHZ /2GO memory )

Is my memory faulty on what it used to be ? is this "expected" ? 
(or has data increase by a factor 10 ?)

-- 
sly 
Sylvain Letuffe liste at letuffe.org
qui suis-je : http://slyserv.dyndns.org