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Make pmap_is_prefaultable() more TLB friendly. Specifically, make it use

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the kernel's direct map instead of the pmap's recursive mapping to access
the lowest level in the page table.  The direct map is preferable for two
reasons: (1) The TLB is more likely to hold the required direct mapping
because pmap_enter() has already used the direct map to access a nearby
PTE and (2) loading a direct mapping into the TLB involves walking only 2
or 3 levels of the page table instead of 4.
This commit is contained in:
alc 2008-01-14 21:25:06 +00:00
parent 00c36da743
commit 021a700f2a
1 changed files with 1 additions and 1 deletions
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2
sys/amd64/amd64/pmap.c
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@ -3104,7 +3104,7 @@ pmap_is_prefaultable(pmap_t pmap, vm_offset_t addr)
PMAP_LOCK(pmap);
pde = pmap_pde(pmap, addr);
if (pde != NULL && (*pde & PG_V)) {
pte = vtopte(addr);
pte = pmap_pde_to_pte(pde, addr);
rv = (*pte & PG_V) == 0;
}
PMAP_UNLOCK(pmap);