RFC: Add getcpu wrapper

["H.J. Lu" <hjl dot tools at gmail dot com>]

To optimize for multi-node NUMA system, I need a very fast way to identity which
node the current process is running on.  getcpu:

NAME
       getcpu  -  determine  CPU  and NUMA node on which the calling thread is
       running

SYNOPSIS
       #include <linux/getcpu.h>

       int getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache);

       Note: There is no glibc wrapper for this system call; see NOTES.

DESCRIPTION
       The getcpu() system call identifies the processor and node on which the
       calling thread or process is currently running and writes them into the
       integers pointed to by the cpu and node arguments.  The processor is  a
       unique  small  integer  identifying  a CPU.  The node is a unique small
       identifier identifying a NUMA node.  When either cpu or  node  is  NULL
       nothing is written to the respective pointer.

returns such info.  But syscall () is too slow.  I'd like to add a wrapper to
glibc.   Any comments?

Thanks.

-- 
H.J.