I'm wondering if it is a good idea in __alloc_pages to first try to see
if a order 0 request can be serviced by cpu's pcp before checking the
low water marks for the zone. The is useful if a request can be
serviced by a free page on the pcp then there is no reason to check the
zone's limits. This early allocation should be without any replenishing
of pcps from zone free list
thanks,
-rohit