[OpenLayers-Dev] Mod_tile performance enhancements?

[Jason Lee]

Hi,
I have mod_tile running on a dedicated Linux server (Ubuntu 11.04, 24GB
RAM, 8 virtual QuadCore i7 processors) and generating some custom maps. I
am using ab (Apache Bench) to benchmark its performance when rendering new
tiles (at zooms 17-18, 1 concurrent x 1 run, clearing cache each time) and
getting time around 10,000 ms (10 secs) per tile. Thereafter it is very
quick (100ms) because it is cached.

Ten seconds does sound quite slow and I was wondering what can be done to
improve it. Just out of curiosity, I tried disabling all the 7 Layers
except for 1 Layer in the Mapnik stylesheet, so the rendering requires a
lot less db querying and map rendering - but I'm still getting 10 seconds
performance. This would suggest that the performance bottleneck is not
related to the mapnik backend.

I've also played around with increasing the NUM_THREADS=3 to 32 in the
renderd.conf, but still no significant performance improvement when
rendering a fresh tile. Any ideas or pointers would be welcome. Thanks

Jason
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