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Optimize pmap_remove()'s handling of PG_G mappings. Specifically,

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instead of calling pmap_invalidate_page() for each PG_G mapping, call
pmap_invalidate_range() for each range of PG_G mappings.  In addition,
eliminate a redundant call to pmap_invalidate_page().  Both
pmap_remove_pte() and pmap_remove_page() called pmap_invalidate_page()
when the mapping had the PG_G attribute.  Now, only pmap_remove_page()
calls pmap_invalidate_page().  Altogether, these changes eliminate 53%
of the TLB shootdowns for a "buildworld" on a ZFS file system.  On
FFS, the reduction is 3%.

MFC after:	6 weeks
This commit is contained in:
Alan Cox 2010-07-15 16:25:51 +00:00
parent 71ad35a185
commit 7db39bcb05
1 changed files with 15 additions and 14 deletions
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29
sys/amd64/amd64/pmap.c
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@ -2602,12 +2602,6 @@ pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t va,
oldpte = pte_load_clear(ptq);
if (oldpte & PG_W)
pmap->pm_stats.wired_count -= 1;
/*
* Machines that don't support invlpg, also don't support
* PG_G.
*/
if (oldpte & PG_G)
pmap_invalidate_page(kernel_pmap, va);
pmap_resident_count_dec(pmap, 1);
if (oldpte & PG_MANAGED) {
m = PHYS_TO_VM_PAGE(oldpte & PG_FRAME);
@ -2647,7 +2641,7 @@ pmap_remove_page(pmap_t pmap, vm_offset_t va, pd_entry_t *pde, vm_page_t *free)
void
pmap_remove(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
{
vm_offset_t va_next;
vm_offset_t va, va_next;
pml4_entry_t *pml4e;
pdp_entry_t *pdpe;
pd_entry_t ptpaddr, *pde;
@ -2748,20 +2742,27 @@ pmap_remove(pmap_t pmap, vm_offset_t sva, vm_offset_t eva)
if (va_next > eva)
va_next = eva;
va = va_next;
for (pte = pmap_pde_to_pte(pde, sva); sva != va_next; pte++,
sva += PAGE_SIZE) {
if (*pte == 0)
if (*pte == 0) {
if (va != va_next) {
pmap_invalidate_range(pmap, va, sva);
va = va_next;
}
continue;
/*
* The TLB entry for a PG_G mapping is invalidated
* by pmap_remove_pte().
*/
}
if ((*pte & PG_G) == 0)
anyvalid = 1;
if (pmap_remove_pte(pmap, pte, sva, ptpaddr, &free))
else if (va == va_next)
va = sva;
if (pmap_remove_pte(pmap, pte, sva, ptpaddr, &free)) {
sva += PAGE_SIZE;
break;
}
}
if (va != va_next)
pmap_invalidate_range(pmap, va, sva);
}
out:
if (anyvalid)