Comment 12 for bug 1917203

On 4/10/2021 5:03 PM, David Coe wrote:
> Results for AMD Ryzen 4700U running Ubuntu 21.04β kernel 5.11.0-13
>
> $ sudo dmesg | grep IOMMU
> [    0.490352] pci 0000:00:00.2: AMD-Vi: IOMMU performance counters supported
> [    0.491985] pci 0000:00:00.2: AMD-Vi: Found IOMMU cap 0x40
> [    0.493732] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank).
> [    0.793259] AMD-Vi: AMD IOMMUv2 driver by Joerg Roedel <email address hidden>
>
> ....
>
> $ sudo perf stat -e 'amd_iommu_0/cmd_processed/, amd_iommu_0/cmd_processed_inv/, amd_iommu_0/ign_rd_wr_mmio_1ff8h/, amd_iommu_0/int_dte_hit/, amd_iommu_0/int_dte_mis/, amd_iommu_0/mem_dte_hit/, amd_iommu_0/mem_dte_mis/, amd_iommu_0/mem_iommu_tlb_pde_hit/, amd_iommu_0/mem_iommu_tlb_pde_mis/, amd_iommu_0/mem_iommu_tlb_pte_hit/, amd_iommu_0/mem_iommu_tlb_pte_mis/, amd_iommu_0/mem_pass_excl/, amd_iommu_0/mem_pass_pretrans/, amd_iommu_0/mem_pass_untrans/, amd_iommu_0/mem_target_abort/,
> amd_iommu_0/mem_trans_total/, amd_iommu_0/page_tbl_read_gst/, amd_iommu_0/page_tbl_read_nst/, amd_iommu_0/page_tbl_read_tot/, amd_iommu_0/smi_blk/, amd_iommu_0/smi_recv/, amd_iommu_0/tlb_inv/, amd_iommu_0/vapic_int_guest/, amd_iommu_0/vapic_int_non_guest/' sleep 10
>
> Performance counter stats for 'system wide':
>
>                12      amd_iommu_0/cmd_processed/             (33.28%)
>                 6       amd_iommu_0/cmd_processed_inv/        (33.32%)
>                 0       amd_iommu_0/ign_rd_wr_mmio_1ff8h/     (33.36%)
>               290       amd_iommu_0/int_dte_hit/              (33.40%)
>                20       amd_iommu_0/int_dte_mis/              (33.46%)
>               391       amd_iommu_0/mem_dte_hit/              (33.49%)
>             3,720       amd_iommu_0/mem_dte_mis/              (33.49%)
>                44       amd_iommu_0/mem_iommu_tlb_pde_hit/    (33.46%)
>               810       amd_iommu_0/mem_iommu_tlb_pde_mis/    (33.45%)
>                35       amd_iommu_0/mem_iommu_tlb_pte_hit/    (33.41%)
>               746       amd_iommu_0/mem_iommu_tlb_pte_mis/    (33.37%)
>                 0       amd_iommu_0/mem_pass_excl/            (33.32%)
>                 0       amd_iommu_0/mem_pass_pretrans/        (33.28%)
>                 0       amd_iommu_0/mem_pass_untrans/         (33.28%)
>                 0       amd_iommu_0/mem_target_abort/         (33.27%)
>               715       amd_iommu_0/mem_trans_total/          (33.27%)
>                 0       amd_iommu_0/page_tbl_read_gst/        (33.28%)
>                36       amd_iommu_0/page_tbl_read_nst/        (33.27%)
>                36       amd_iommu_0/page_tbl_read_tot/        (33.27%)
>                 0       amd_iommu_0/smi_blk/                  (33.28%)
>                 0       amd_iommu_0/smi_recv/                 (33.26%)
>                 0       amd_iommu_0/tlb_inv/                  (33.23%)
>                 0       amd_iommu_0/vapic_int_guest/          (33.24%)
>               366       amd_iommu_0/vapic_int_non_guest/      (33.27%)
>
> The immediately obvious difference is the with the enormous count seen on mem_dte_mis on the older Ryzen 2400G. Will do some RTFM but anyone with comments and insight?
>
> 841,689,151,202,939       amd_iommu_0/mem_dte_mis/              (33.44%)
>
> Otherwise, all seems to running smoothly (especially for a distribution still in β). Bravo and many thanks all!
>
That doesn't look correct. Lemme do some more investigation also.

Thanks,
Suravee