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amd64: fix user pt_page accounting

Authored by alc on Dec 5 2021, 6:50 PM.



When a superpage mapping is destroyed and the original page table page containing 4KB mappings that was being held in reserve is deallocated, the pt_page count was not being decremented. Consequentially, the user pt_count would grow over time.

Test Plan

For example, after multiple iterations of "buildworld", I was seeing the following illogical counts:

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

Diff Detail

rG FreeBSD src repository
Automatic diff as part of commit; lint not applicable.
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

alc requested review of this revision.Dec 5 2021, 6:50 PM
alc created this revision.
This revision is now accepted and ready to land.Dec 5 2021, 6:56 PM
This revision was automatically updated to reflect the committed changes.