[MS4W-Users] Parallelism in KaMap - an Apache and Php/Mapscript configuration question

Jeff Dege 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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