[$] A memory allocator for BPF code

Loading a BPF program into the kernel involves a lot of steps, including
verification, permissions checking, linking to in-kernel helper functions,
and compilation to the native instruction format. Underneath all of that,
though, lies one other simple task: allocating some memory to store the
compiled BPF program in the kernel's address space. It turns out that this
allocation
can be somewhat wasteful of memory in current kernels, especially on
systems where large numbers of BPF programs are loaded. This
patch set from Song Liu seeks to remedy this problem by introducing yet
another specialized memory allocator into the kernel.