[mapserver-dev] More Performance

[Paul Ramsey]

Andrea Aime pointed out that Geoserver is still running about 3-times
as fast as Mapserver in some use cases, which has prompted me to
discover Shark (note to developers on OS/X, learn to run Shark).

Among the things Shark tells me is that the epsg configuration file
remains the biggest (avoidable, but non-obvious) performance issue,
potentially hogging huge amounts of resources, since the projections
are loaded even for layers that aren't being rendered.  Even worse,
it's a performance issue that fcgi doesn't fix, since the loading
happens in msLoadMap.

Another thing Shark tells me is that we are burning resources in
curl_global_init (called from msHTTPInit via msHTTPInitRequestObj)
even when there are no WMS or WFS layers defined.  This is eating
about 5% of the total cycles, on a fairly well-tuned map file, and
could be fixed.

Finally, the biggest single resource muncher in this small-easy-map
case is loading the font file.  This could be an artefact of the OS/X
font loading, or it could be generic. It looks like gd has a font
cache, so perhaps this goes away in FCGI.  I guess that should be my
next test, because if it doesn't go away it's a big win in the FCGI
case to make it go away.

P.
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