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

[Ravi Bangoria <ravi.bangoria@amd.com>]

On 10-Nov-26 8:52 AM, Hang Zhengyang wrote:
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> 
> 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@gmail.com>
> 
> 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.)

Adding Vasant, as he is more familiar with the IOMMU PMU area.