managing pages from different address ranges. Generally speaking, this
feature is used to increase the likelihood that physical pages are
available that can meet special DMA requirements or can be accessed through
a limited-coverage direct mapping (e.g., MIPS). However, prior to this
change, the configuration of the free lists was static, i.e., it was
determined at compile time. Consequentally, free lists could be created
for address ranges that held no actual pages, for example, on 32-bit MIPS-
based systems with 512 MB or less of physical memory. This change makes
the creation of the free lists dynamic, i.e., it is based on the available
physical memory at boot time.
On 64-bit x86-based systems with 64 GB or more of physical memory, create
free lists for managing pages with physical addresses below 4 GB. This
change is to address reported problems with initializing devices that
require the allocation of physical pages below 4 GB on some systems with
128 GB or more of physical memory.
PR: 185727
Differential Revision: https://reviews.freebsd.org/D1274
Reviewed by: jhb, kib
MFC after: 3 weeks
Sponsored by: EMC / Isilon Storage Division
369e66acd7