Instead of downloading a font each time it is requested by a client, the X server attempts to temporarily store the font in the portion of memory called the font cache. Font caching improves the performance of clients that use large numbers of fonts.
After a font is closed by the last client using it, the font is added to the font cache instead of being freed. When the font is requested again, it is taken from the cache instead of being read from a host.
The font cache is flushed when the X server is reset and when the font path is changed. When the font cache is full, the oldest resident font is replaced with the latest font being inserted into the cache. If the server runs low on memory, it will start reclaiming memory from the cache.
To change the size of the font cache, specify the size (in bytes) in the xserver-font-cache-max-size parameter (Setup -> Change Setup Parameters -> Fonts -> Font Cache Maximum Size). The new font cache size takes effect immediately after an apply command is entered.
Table 7-7 xserver-font-cache-max-size Parameter
Up to the specified number of bytes are used for caching fonts. Range: 0 - 4294967295.