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Microoptimize amd64/pmap.c pmap_protect_pde().

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For the loop that dirties vm_pages in case superpage was written to,
check the complete condition before the loop.

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2017-02-19 03:33:20 +00:00
parent e2a8d17887
commit d9440197b4
1 changed files with 3 additions and 3 deletions
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6
sys/amd64/amd64/pmap.c
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@ -3998,12 +3998,12 @@ pmap_protect_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t sva, vm_prot_t prot)
anychanged = FALSE;
retry:
oldpde = newpde = *pde;
if (oldpde & PG_MANAGED) {
if ((oldpde & (PG_MANAGED | PG_M | PG_RW)) ==
(PG_MANAGED | PG_M | PG_RW)) {
eva = sva + NBPDR;
for (va = sva, m = PHYS_TO_VM_PAGE(oldpde & PG_PS_FRAME);
va < eva; va += PAGE_SIZE, m++)
if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW))
vm_page_dirty(m);
vm_page_dirty(m);
}
if ((prot & VM_PROT_WRITE) == 0)
newpde &= ~(PG_RW | PG_M);