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authorDan McGee <dan@archlinux.org>2011-07-19 04:47:29 -0500
committerDan McGee <dan@archlinux.org>2011-07-21 15:04:30 -0500
commitbb3dada8711fbb822513cd556167867b537f8986 (patch)
tree1230de6f94675777e9cdd4150779f4756995efa1 /contrib/README
parent058ee1737182c2d5e900e0feba57f0d6496e735e (diff)
Convert package filelists to an array instead of linked list
This accomplishes quite a few things with one rather invasive change. 1. Iteration is much more performant, due to a reduction in pointer chasing and linear item access. 2. Data structures are smaller- we no longer have the overhead of the linked list as the file struts are now laid out consecutively in memory. 3. Memory allocation has been massively reworked. Before, we would allocate three different pieces of memory per file item- the list struct, the file struct, and the copied filename. What this resulted in was massive fragmentation of memory when loading filelists since the memory allocator had to leave holes all over the place. The new situation here now removes the need for any list item allocation; allocates the file structs in contiguous memory (and reallocs as necessary), leaving only the strings as individually allocated. Tests using valgrind (massif) show some pretty significant memory reductions on the worst case `pacman -Ql > /dev/null` (366387 files on my machine): Before: Peak heap: 54,416,024 B Useful heap: 36,840,692 B Extra heap: 17,575,332 B After: Peak heap: 38,004,352 B Useful heap: 28,101,347 B Extra heap: 9,903,005 B Several small helper methods have been introduced, including a list to array conversion helper as well as a filelist merge sort that works directly on arrays. Signed-off-by: Dan McGee <dan@archlinux.org>
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