linux-kernel - Re: [PATCH 2/2] iommu/amd: Remove performance counter pre-initialization test

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Date:   Tue, 13 Apr 2021 20:51:56 +0700
From:   "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To:     David Coe <david.coe@...e.co.uk>, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org
Cc:     joro@...tes.org, will@...nel.org, jsnitsel@...hat.com,
        pmenzel@...gen.mpg.de, Jon.Grimm@....com,
        Tj <ml.linux@...oe.vision>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Alexander Monakov <amonakov@...ras.ru>,
        Alex Hung <1917203@...s.launchpad.net>
Subject: Re: [PATCH 2/2] iommu/amd: Remove performance counter
 pre-initialization test



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 <jroedel@...e.de>
> 
> ....
> 
> $ 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