[MS4W-Users] Parallelism in KaMap - an Apache and Php/Mapscript configuration question
jeff.dege at korterra.com
Thu Nov 11 14:09:48 EST 2010
Daniel Morissette wrote:
> > Jeff Dege wrote:
> > Actually, even using KaMap, the tile generation is too slow, so to get
> > acceptable performance we need to precache the tiles. We have a
> > program that generates a series of "wget http://..../tile.php?..."
> > calls, each of which hits the php app on the Apache webserver, asking
> > for a particular tile. Php checks its disk cache, and if the tile
> > exists, it returns it. If not, it makes a call to mapscript to
> > generate the image, saves it in its disk cache, and returns the generated image.
> > Running the six batch files simultaneously took 37 hours to complete.
> > Running just one of them took a bit over seven hours. That's way too
> > close to 1/6^th of the time for me to not think that we've got a
> > bottleneck, somewhere, and there's no parallelism happening.
> Does your list of tile URLs contain only one tile URL per metatile or does it contain a list of possible tiles in a given area, resulting in > > multiple hits on the same metatile?
The different batch files contained URLS at different zoom levels. We weren't locking because of simultaneous access to the same metatile.
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