MEDx Frequently Asked Questions - MEDx Configuration

Q: What is the Tile Pool?

MEDx reserves a fixed amount of memory for image data. This block of memory is referred to as the tile pool memory. When a file is initially read into MEDx, only those slices that are needed for display purposes are actually loaded into the tile pool. Only when you go to the volume page (to see or display the volume) or refer to it for an image processing operation are the slices read in from the image file.

The data is read in using a tiled structure (with each slice being a tile of data). It is this Tile Pool memory that is used when reading in the tiles of a data set(s). This memory is allocated ALL AT ONCE when the first dataset is read in to MEDx and is used thereafter for any more datasets that are read into MEDx.

If a particular slice has not been modified by an operation then MEDx can simply remove the slice from the tile pool since the original version (aka. zero'th version) of this slice that is on disk in the file that it was read from. If on the other hand a particular slice has been modified by an operation then MEDx cannot use the zero'th version of this slice that is on disk since it no longer has the correct image data. In this case, when the tile pool fills up and a slice that has been modified needs to be removed from the tile pool then it will be written to a file on disk referred to as the page file.

The page file is essentially an internal swap space for image data. Please note that the Tile Pool memory holds only the tile data and does not hold any other kinds of data allocated by malloc(). Once the Tile Pool memory is filled up, the data is swapped out to a paging file.

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