[ka-Map-users] KaMap performance tuning

[Jeff Dege]

I understand that there is overhead involved, but I see a 10x difference
in performance between running my wget batchfiles with a full cache and
an empty one.

So the overhead isn't in the networking or communications.

> -----Original Message-----
> From: Paul Spencer [mailto:pspencer at dmsolutions.ca] 
> Sent: Tuesday, May 22, 2007 6:56 AM
> To: Jeff Dege
> Cc: ka-map-users at lists.maptools.org
> Subject: Re: [ka-Map-users] KaMap performance tuning
> 
> Hi Jeff,
> 
> this is an interesting analysis.  For the record, I always thought  
> properly tuned shapefiles (tiled, indexed, sorted) were faster than  
> any other format.
>
> I suspect that the actual map rendering time relative to the other  
> processes involved (as you said, Apache, PHP and also the PHP code  
> that slices the resulting image, plus using wget invokes a network  
> stack and various other communications pieces) is fairly  
> insignificant in your case (and perhaps in general).  I don't really  
> know of a good way to isolate the various factors.  Well, you could  
> look into using xdebug with PHP and invoking tile.php 
> directly to see  
> what the overhead is.
> 
> If this is the case, it would be awesome to have a custom libmap  
> executable that could take the place of tile.php - essentially a C  
> program (preferably that could run either on command line or as cgi)  
> that would create tiles built on top of the mapserver C API (such as  
> it is).  Given the simplicity of the task, any scripted approach  
> (such as tile.php) is going to be less than optimal.
> 
> Any volunteers?
> 
> Paul
> 
> 
> On 21-May-07, at 3:25 PM, Jeff Dege wrote:
> 
> > We've been using KaMap with Mapserver and OpenLayers, with some  
> > success.
> > We've recently begin looking at using PostGIS instead of shapefiles,
> > hoping to getter performance when generating maps that haven't yet  
> > been
> > tiled.
> >
> > So we loaded our shapefiles into PostGIS tables, and 
> created a new map
> > file that was a copy of the first, except that it got its map data  
> > from
> > the PostGIS tables.
> >
> > Our first comparison was using shp2img, which showed a dramatic  
> > decrease
> > in the time needed to generate maps - with our data, 
> PostGIS was eight
> > to ten times faster.
> >
> > So we cleared out our tile cache, pointed KaMap at the PostGIS map  
> > file,
> > and saw very little difference.
> >
> > So we created a batch file that would download a thousand different
> > tiles, using wget to make direct calls against tile.php, 
> and timed how
> > long it took to run, with the shapefile and the PostGIS map 
> files.   
> > The
> > PostGIS test was only five percent that the shapefile test.
> >
> > So we created yet another batch file that used wget to make direct  
> > calls
> > against mapserver.exe, running in CGI mode.  When 
> generating maps from
> > PostGIS data, mapserver was eight times faster than against  
> > shapefiles.
> >
> > So now the question:  If the image creation is so much faster, when
> > accessed through shp2img, and when accessed through 
> mapserver.exe, why
> > is that speed improvement not visible when loading tiles through  
> > kamap's
> > tile.php?
> >
> > It's clear to me that there must be some bottleneck, reducing
> > performance.  My guess would be in Apache or PHP configuration.
> >
> > Does anyone know how I can measure what time is being spent doing  
> > what,
> > in this area?  What configuration options I should look at, 
> to try to
> > improve performance?
> >
> > Thanks.
> >
> >
> > _______________________________________________
> > ka-Map-users mailing list
> > ka-Map-users at lists.maptools.org
> > http://lists.maptools.org/mailman/listinfo/ka-map-users
> 
> +-----------------------------------------------------------------+
> |Paul Spencer                          pspencer at dmsolutions.ca    |
> +-----------------------------------------------------------------+
> |Chief Technology Officer                                         |
> |DM Solutions Group Inc                http://www.dmsolutions.ca/ |
> +-----------------------------------------------------------------+
> 
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