We are running GeoServer 2.15 and we keep seeing this warning message on some pages saying "The "Coverage Access" page "ImageIO Cache Memory Threshold" is unset, and can cause a severe performance penalty when seeding tiles. A value of 1024K should suffice for the most common tile sizes."
While there doesn't seem to be a "Coverage Access" page, there is a "Raster Access" page with a setting for "ImageIO cache memory threshold (KB)" but no matter what we set that to and click Submit, the warning refuses to go away. What are we doing wrong here?