- PGA_WRITEABLE indicates that there *might be* a writable mapping for the
particular page, so to avoid frequent sweeping of the pv_entries whenever
pmap_nuke_pv(), pmap_modify_pv(), etc. is called, it is sufficient to
clear that flag if there are no managed mappings for that page anymore
(notice that only pmap_enter is authorized to set this flag).
- Avoid redundant checking for PVF_WIRED flag when this flag cannot be set
anyway.
- Clear PGA_WRITEABLE only once for each vm_page instead of multiple,
redundant clearing it in loop when there are no writeable mappings
to that page anymore.
Submitted by: Zbigniew Bodek <zbb@semihalf.com>
Reviewed by: gber
Sponsored by: The FreeBSD Foundation, Semihalf
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