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5.6.4 Performance Tuning
Performance Tuning
If you are running into issues with memory consumption or slow response of the IDV, there are several things you can do.
The amount of memory used by the IDV will depend on the size of the datasets you use and the types of displays. Datasets rendered as 2D depictions (plan views - contours or color shaded displays) use much less memory than 3D displays (isosurfaces, cross sections). Large datasets (images, dense grids) will use much more memory.

There are several features in the IDV that allow you to more efficiently view large datasets:

Temporal/Spatial Subset of Data Some data sources allow you to subset the data temporally and spatially. You can set these properties for all fields in a dataset through the Properties menu of the data source (double click on the Data Source in the Field Selector) or you can set these for individual field using the tabs in the lower right corner of the Field Selector. For more information, see the Data Source Properties section of the IDV User's Guide. Memory allocation By default, the IDV startup script (runIDV) allocates 512 megabytes of maximum memory for Java. This is usually the optimum amount for a Windows system with 1 gigabyte of physical memory (RAM). Windows takes up half of that anyway and once Windows has to start swapping, performance severely degrades. On a Linux system, you can probably get away with 700m for 1 Gb of memory as it does a much better job of swapping. All this also depends on what else you are running on the machine and how much memory those applications use.

If your system has more than 1 Gb of memory, increasing the amount available to the IDV can improve performance for displaying large datasets. You can change the runIDV script to increase the amount of memory. In that script, change the -Xmx512m to some higher number (e.g. -Xmx1024m). The number is the number of bytes, the trailing m is a multiplier (m=mega). Do not use the maximum amount of memory on your machine as some is needed for the operating system itself. If the system has to use swap memory, performance will degrade as well. For a system with 2 Gb of physical memory, you can probably allocate 1.5 Gb to the IDV. If you have less than 1 Gb of RAM, you should start the IDV with about 1/2 of the total memory (e.g., if your system has only 512 megabytes of RAM, you should use -Xmx256m).

Data Caching By default, the IDV caches the data used for a display in memory. If a field is used more than once for several displays, caching the data prevents an additional reading from of the data from disk or a remote server. If you are only displaying/using a field (i.e. not using it for multiple displays or calculations), you can keep the IDV from caching it in memory. You can turn off data caching by unchecking the Cache data in memory checkbox on the Data & Formats tab of the user preferences (accessible from the Edit->Preferences menu). Maximum grid/image size You can also set the maximum size of a grid or image that will be displayed. This will allow you to download a large image or grid, but it will be re-sampled before displaying if it is larger than the maximum size you have asked for. You can set the maximum image/grid size under the Data & Formats tab of the user preferences (accessible from the Edit->Preferences menu). Fast Rendering By default, the IDV will try to adjust the data renderings to account for projection seams. This is computationally intensive in some cases and slows down the display of data. When you set your preference to "Use Fast Rendering" (under the General tab of the user preferences (Edit->Preferences menu)), the IDV will not try to account for the projection seams. If you are displaying data in its native projection, this will result in faster rendering of the data depiction. However, if you have several displays of data, each from a different data source and on a different projection, you may see anomalies in the displays (spurious lines, portions of images). At that point, you can turn off fast rendering for a particular display using the Edit->Properties menu of the Display Control for that display, or set your system preference back to not use fast rendering.

 


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U09-NRM-127: The role of Distributed Data Access Technologies in NRM - for ITC-IDV version 2.7 > Advanced Topics > Miscellaneous Items