* Convert ABD to use the Linux Kernel scatterlist implementation
instead of the hand rolled one from illumos.
* Scatter ABDs are preferentially populated with higher order
compound pages from a single zone. Allocation size is
progressively decreased until it can be satisfied without
performing reclaim or compaction.
* An alternate page allocator is provided for kernels older
than 3.6 and for CONFIG_HIGHMEM systems. This allocator
is designed as a fallback for maximum compatibility.
* Extended abdstats to provide visibility in the the allocator.
* Add cached value for PAGESIZE in userspace.
Contributions-by:
Chunwei Chen <david.chen@osnexus.com>
Gvozden Neskovic <neskovic@gmail.com>
Jinshan Xiong <jinshan.xiong@intel.com>
Isaac Huang <he.huang@intel.com>
David Quigley <david.quigley@intel.com>
Brian Behlendorf <behlendorf1@llnl.gov>
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