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Apply a small optimization to pmap_remove_l3_range(). Specifically, hoist a

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PHYS_TO_VM_PAGE() operation that always returns the same vm_page_t out of
the loop.  (Since arm64 is configured as VM_PHYSSEG_SPARSE, the
implementation of PHYS_TO_VM_PAGE() is more costly than that of
VM_PHYSSEG_DENSE platforms, like amd64.)

MFC after:	1 week
This commit is contained in:
Alan Cox 2019-12-15 22:41:57 +00:00
parent 3c2db0ef43
commit 68ca966558
1 changed files with 4 additions and 2 deletions
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6
sys/arm64/arm64/pmap.c
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@ -2616,11 +2616,13 @@ pmap_remove_l3_range(pmap_t pmap, pd_entry_t l2e, vm_offset_t sva,
struct rwlock *new_lock;
pt_entry_t *l3, old_l3;
vm_offset_t va;
vm_page_t m;
vm_page_t l3pg, m;
PMAP_LOCK_ASSERT(pmap, MA_OWNED);
KASSERT(rounddown2(sva, L2_SIZE) + L2_SIZE == roundup2(eva, L2_SIZE),
("pmap_remove_l3_range: range crosses an L3 page table boundary"));
l3pg = sva < VM_MAXUSER_ADDRESS ? PHYS_TO_VM_PAGE(l2e & ~ATTR_MASK) :
NULL;
va = eva;
for (l3 = pmap_l2_to_l3(&l2e, sva); sva != eva; l3++, sva += L3_SIZE) {
if (!pmap_l3_valid(pmap_load(l3))) {
@ -2671,7 +2673,7 @@ pmap_remove_l3_range(pmap_t pmap, pd_entry_t l2e, vm_offset_t sva,
}
if (va == eva)
va = sva;
if (pmap_unuse_pt(pmap, sva, l2e, free)) {
if (l3pg != NULL && pmap_unwire_l3(pmap, sva, l3pg, free)) {
sva += L3_SIZE;
break;
}