Re: [PATCH v2 0/2] perf jevents: Add IOMMU PTW & device entry metrics

[Hang Zhengyang]

On Mon, 02 Nov 2026 21:14:15 +0000, Jacob Lefkowitz wrote:
> Adds AMD specific metrics for the IOMMU with respect to page table
> walks and device table entires.

Tested on Zen 3 (Ryzen 7 PRO 5850U) on top of perf-tools-next
13a8d580433a.  Both groups show up and count, perf test 130 and 131
pass, and under O_DIRECT reads from NVMe the values match the raw
amd_iommu_0 counts.

Tested-by: Hang Zhengyang <hang.zhengyang1010@xxxxxxxxx>

Two values look odd on this machine:

 - lpm_iommu_ptw_nested_read_ratio is 100% with no guest running:
   page_tbl_read_nst equals page_tbl_read_tot.

 - lpm_iommu_ptw_reads_per_tlb_miss is about 0.2: 142588 page table
   reads against 440805 pte and 192018 pde misses.

Ravi, are these expected on Zen 3?

(Tested with the help of an AI assistant; I checked the results.)