[$] Making slab-allocated objects movable

Memory fragmentation is a constant problem for memory-management
subsystems. Over the years, considerable effort has been put into
reducing fragmentation in the Linux kernel, but almost all of that work has
been focused on memory management at the page level. The slab allocators,
which (mostly) manage memory in chunks of less than the page size, have
seen less attention, but fragmentation at this level can create problems
throughout the system. The slab
movable objects patch set posted by Tobin Harding is an attempt to
improve this situation by making it possible for the kernel to actively
defragment slab pages by moving objects around.