This patch: http://plam.csail.mit.edu/~plam/tmp/fontconfig-mmap-050609.diff modifies fontconfig's CVS HEAD to use an mmap()able file containing internal fontconfig data structures. The new binary fc-mmap creates this map file (in /tmp, for now[1]) and fontconfig clients use this map file instead of loading font data themselves. On my system, my modified version of fontconfig mmaps 147786 bytes into memory (instead of creating around 100k of dynamic data structures). I believe that this patch is stable; it produces no differences in behaviour as compared to a stock fontconfig under my tests. The public API modified the patch is a pair of functions, FcMmapForce() and FcMmapSave(). FcMmapForce(true) forces fontconfig to ignore any mmaping data which might exist, and FcMmapSave() is used in fc-mmap to write the data structures to disk. Unlike an earlier version of the patch, no other API modifications are necessary. The structure of the patch is as follows. 1. Loading: I include a new file, src/fcmmap.c, which contains the bulk of the logic for reading and writing the mmap file; some logic lives in src/fclang.c (to serialize a data structure private to that file). During fontconfig's initialization, it first calls FcMmapLoadObjects immediately after opening the configuration file, but before processing it, to load string constants into memory. Later on, fontconfig calls FcMmapLoadFonts to mmap the rest of the mmapped data into memory, instead of loading the data from the font files. 2. Saving: I use a three-phase algorithm to save the data to disk. In the first phase (initiated by FcMmapSave's call to FcFontSetSerialize(config)), I move all font information reachable from currentConfig.fonts to a set of static arrays (with a first relocation from the dynamic addresses to the static arrays). Next, I write the data to the candidate mmap file. The final phase is the fixup; I use mmap() to read the data back into memory, recording the addresses given to me by mmap() to, again, relocate internal pointers as appropriate. Once fixup is complete, the mmap file is ready to be loaded with no further transformations. Thanks to Sylvain Fourmanoit for hints on how to improve an earlier version of this patch. I would like this patch to be considered for inclusion in the fontconfig CVS. pat [1] I would appreciate any suggestions on where the map file should be created. It is difficult to put the map file's location in the configuration file, because the map file is needed before fontconfig loads the configuration information.
