Correct two pessimizations in pmap_extract_and_hold(). Test the PTE for
having PTE_RO set instead of PTE_D. This avoids some unnecessary failures by pmap_extract_and_hold() that will have to be handled by a call to vm_fault_hold(). Testing the PTE for both being non-zero and having PTE_V set is redundant. The latter suffices.
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parent
5847daf4c2
commit
948aea4031
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=241276
@ -791,24 +791,25 @@ pmap_extract(pmap_t pmap, vm_offset_t va)
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vm_page_t
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pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot)
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{
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pt_entry_t *ptep;
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pt_entry_t pte;
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pt_entry_t pte, *ptep;
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vm_paddr_t pa, pte_pa;
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vm_page_t m;
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vm_paddr_t pa;
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m = NULL;
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pa = 0;
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PMAP_LOCK(pmap);
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retry:
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ptep = pmap_pte(pmap, va);
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if ((ptep != NULL) && ((pte = *ptep) != 0) &&
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pte_test(&pte, PTE_V) &&
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(pte_test(&pte, PTE_D) || (prot & VM_PROT_WRITE) == 0)) {
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if (vm_page_pa_tryrelock(pmap, TLBLO_PTE_TO_PA(pte), &pa))
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goto retry;
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m = PHYS_TO_VM_PAGE(TLBLO_PTE_TO_PA(pte));
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vm_page_hold(m);
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if (ptep != NULL) {
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pte = *ptep;
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if (pte_test(&pte, PTE_V) && (!pte_test(&pte, PTE_RO) ||
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(prot & VM_PROT_WRITE) == 0)) {
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pte_pa = TLBLO_PTE_TO_PA(pte);
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if (vm_page_pa_tryrelock(pmap, pte_pa, &pa))
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goto retry;
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m = PHYS_TO_VM_PAGE(pte_pa);
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vm_page_hold(m);
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}
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}
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PA_UNLOCK_COND(pa);
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PMAP_UNLOCK(pmap);
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