[OSM-dev] mod_tile performance enhancements?

[Dane Springmeyer]

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 <frederik at 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
> 
> 
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