alibaba/tengine — pull request #468 by chobits (2014-06-18 02:45:33+00:00)
Title: slab allocator free pages defragmentation

Large allocations from a slab pool result in free page blocks being fragmented,
eventually leading to a situation when no further allocation larger than a page
size are possible from the pool. While this isn't a problem for nginx itself,
it is known to be bad for various 3rd party modules. Fix is to merge adjacent
blocks of free pages in the ngx_slab_free_pages() function.

Merge nginx official patch.
patch: http://hg.nginx.org/nginx/rev/c46657e391a3
discussion: http://forum.nginx.org/read.php?29,250019