Michael Bedward ha scritto: > Hi Andrea, Jody, > > I'm reworking the RenderingExecutor class in the swing module. At > present, RenderingExecutor is designed to work with one map pane, > running one rendering task at a time. In the new swing code > RenderingExecutor will offer multiple threads (from a cached thread > pool) and be able to work with more than one map pane. My main reason > for doing this is to allow for "linked" panes... > > http://jira.codehaus.org/browse/GEOT-3106 > > I have a dim memory of the two of you discussing multithreaded > rendering for better performance. Is this something that would be > useful to allow for in the new swing code, and if so, how (just in > general terms) ?
Multithreaded rendering has to be dealt with very carefully. Just some random notes: - streaming renderer is not thread safe, if you need to render from multiple threads please use multiple streaming renderers - blindly parallelizing all layer rendering will most likely thrash your machine and make rendering slower. Parallel rendering can improve things if you partition your layers in "zones", where each zone is hitting a different kind of physical resource: one zone for the local machine, one zone for each server you contact. As a rule of thumb never make more than X requests in parallel to the same zone, where X is somewhere between 2 and 6 (the actual value may vary depending on the hardware, network bandwidth and so on). Plus all the renderer will in the end fight for the same set of CPUs on the rendering machine, again, a rule of thumb may be no more than 2 * numcores parallel operations. Parallel rendering also means you'll have to prepare N different rendering surfaces, each one will use memory (eventually lots of it), this gives you another limit to the number of things you can do in parallel. Given you cannot render everything at once a policty to prioritize certain layers might affect how people perceive rendering: - remote layers are slow to render, better start them sooner - small local layers can render fast enough to provide sufficient context for people to keep zooming/panning around without waiting the whole map to be rendered, better start them sooner as well Hope this helps Cheers Andrea -- Andrea Aime OpenGeo - http://opengeo.org Expert service straight from the developers. ------------------------------------------------------------------------------ _______________________________________________ Geotools-devel mailing list Geotools-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-devel
