I've tried searching both the forums and the web at large for this, but it's tricky as most results are parts of log files.
In the forgeChunkLoading.cfg file there is a line to setup a dormantChunkCache. The comments just state that you should "specify the size of that cache." But I'm not clear on what 'size' means. In other words, is it the # of chunks to keep cached? Is it an absolute file size? If so; is it in bytes, kilobytes, megabytes, etc?