I'll add: 1) As you likely know png/zlib compression can be quite slow (and sometimes constitutes a meaningful % of rendering time), so if you are running >= Mapnik 2.0.0 you can use a format string like "png:z=1" to increase encoding time at the slight cost of size. [1]
2) In TileMill we default to 2X metatiles for the usability reason you cite below, but of course its configurable like mod_tile. 3) In Mapnik in current trunk we're currently refactoring core storage of features to make them smaller and faster - this should benefit performance of very large metatiles that pull a big payload. [2] Dane [1] https://github.com/mapnik/mapnik/wiki/OutputFormats [2] https://github.com/mapnik/mapnik/issues/834 On Jan 12, 2012, at 8:18 AM, Jason Lee wrote: > That's a good point, thanks. But from a User Experience point of view - > getting lots of tiles returned in 2's within milliseconds is better than > waiting 10 seconds and then getting a whole bunch of tiles which, once > generated, the user has a better experience panning around - until they reach > another new area to render tiles. > > The experience is rather like WMS vs TMS where you frequently see a blank map > area in WMS. Bearing in mind I am using NUM_THREADS = 32 which means there > are more processors to deal with the higher number of Metatile(2) requests. > > Jason > > > On Thu, Jan 12, 2012 at 2:56 PM, Frederik Ramm <frede...@remote.org> wrote: > Hi, > > > On 01/12/12 14:32, Jason Lee wrote: > I am focusing and playing around with the METATILE parameter and get > performance of 1 tile request :- > > METATILE(16) - 10 secs > METATILE(8) - 3.5 secs > METATILE(4) - 1.5 secs > METATILE(2) - 0.6 secs > > Maybe you are misunderstanding what this means. This means effectively > > METATILE(16) - 10 secs - 256 tiles - 0.039 sec per tile > METATILE(8) - 3.5 secs - 64 tiles - 0.054 sec per tile > METATILE(4) - 1.5 secs - 16 tiles - 0.094 sec per tile > METATILE(2) - 0.6 secs - 4 tiles - 0.150 sec per tile > > > So it seems the best performance for rendering a NEW TILE is to use the > minimum metatile size of 2 (default is 8). > > This is true if you want to render *one tile only*. If however you have an > user behind an OpenLayers client who is likely to requires several > neighbouring tiles, or if you intend to render a large area anyway, then the > larger METATILE numbers give you much better performance. > > Bye > Frederik > > > _______________________________________________ > dev mailing list > dev@openstreetmap.org > http://lists.openstreetmap.org/listinfo/dev > > _______________________________________________ > dev mailing list > dev@openstreetmap.org > http://lists.openstreetmap.org/listinfo/dev
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