The patched attached enables x86_64 xenlinux with "late pin, early

The patched attached enables x86_64 xenlinux with "late pin, early
unpin", which is already implemented for x86_32. Since we now only pin
the root rather than any of the other levels, the overall performance
became better especially with workloads that require heavy memory
management operations.

On 8-way x86_64 xenlinux (dom0) the kernel build was improved by about
10% (using make -j32). Even a small setup like a UP HT system, I see
about 3% performance gain with kernel build (make -j4).

Lmbench also shows improvements in fork/exec/sh:
Processor, Processes - times in microseconds - smaller is better
--------------------------------------------------------------------
Host    OS  Mhz   null null      open slct sig  sig  fork exec sh =20
                  call  I/O stat clos TCP  inst hndl proc proc proc
--------- ------------- ---- ---- ---- ---- ---- ---- ---- ---- ----=20
Linux 2.6.12- 3786 1.13 1.36 3.93 6.04 10.5 1.43 4.33 536. 1446 3614
Linux 2.6.12- 3786 1.13 1.36 3.91 6.03 10.4 1.44 4.38 346. 1050 2831

Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>