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amd64/pmap: fix user page table page accounting

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When a superpage mapping is destroyed and the original page table page
containing 4KB mappings that was being held in reserve is deallocated,
the recently introduced user page table page count was not being
decremented.  Consequentially, the count was wrong and would grow over
time.  For example, after multiple iterations of "buildworld", I was
seeing implausible counts, like the following:

vm.pmap.kernel_pt_page_count: 2184
vm.pmap.user_pt_page_count: 2280849
vm.pmap.pv_page_count: 106

With this change, I now see:

vm.pmap.kernel_pt_page_count: 2183
vm.pmap.user_pt_page_count: 344
vm.pmap.pv_page_count: 105

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D33276
This commit is contained in:
Alan Cox 2021-12-05 17:40:53 -06:00
parent 9f32cb5b1c
commit 4c57d6d555
1 changed files with 2 additions and 2 deletions
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4
sys/amd64/amd64/pmap.c
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@ -6140,7 +6140,7 @@ pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
if (mpte != NULL) {
KASSERT(mpte->valid == VM_PAGE_BITS_ALL,
("pmap_remove_pde: pte page not promoted"));
pmap_resident_count_adj(pmap, -1);
pmap_pt_page_count_adj(pmap, -1);
KASSERT(mpte->ref_count == NPTEPG,
("pmap_remove_pde: pte page ref count error"));
mpte->ref_count = 0;
@ -8408,7 +8408,7 @@ pmap_remove_pages(pmap_t pmap)
if (mpte != NULL) {
KASSERT(mpte->valid == VM_PAGE_BITS_ALL,
("pmap_remove_pages: pte page not promoted"));
pmap_resident_count_adj(pmap, -1);
pmap_pt_page_count_adj(pmap, -1);
KASSERT(mpte->ref_count == NPTEPG,
("pmap_remove_pages: pte page reference count error"));
mpte->ref_count = 0;