From: Rob Clark <robdclark@gmail.com>
To: Johan Hovold <johan@kernel.org>
Cc: Bjorn Andersson <quic_bjorande@quicinc.com>,
Abhinav Kumar <quic_abhinavk@quicinc.com>,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
Sean Paul <sean@poorly.run>,
Marijn Suijten <marijn.suijten@somainline.org>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
Bjorn Andersson <andersson@kernel.org>,
Kuogee Hsieh <quic_khsieh@quicinc.com>,
linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, Doug Anderson <dianders@chromium.org>,
Rob Clark <robdclark@chromium.org>
Subject: Re: [PATCH] drm/msm/dpu: Add missing safe_lut_tbl in sc8280xp catalog
Date: Tue, 31 Oct 2023 05:47:50 -0700 [thread overview]
Message-ID: <CAF6AEGs9PLiCZdJ-g42-bE6f9yMR6cMyKRdWOY5m799vF9o4SQ@mail.gmail.com> (raw)
In-Reply-To: <ZUD0lhStirf8IN8-@hovoldconsulting.com>
On Tue, Oct 31, 2023 at 5:35 AM Johan Hovold <johan@kernel.org> wrote:
>
> On Mon, Oct 30, 2023 at 04:23:20PM -0700, Bjorn Andersson wrote:
> > During USB transfers on the SC8280XP __arm_smmu_tlb_sync() is seen to
> > typically take 1-2ms to complete. As expected this results in poor
> > performance, something that has been mitigated by proposing running the
> > iommu in non-strict mode (boot with iommu.strict=0).
> >
> > This turns out to be related to the SAFE logic, and programming the QOS
> > SAFE values in the DPU (per suggestion from Rob and Doug) reduces the
> > TLB sync time to below 10us, which means significant less time spent
> > with interrupts disabled and a significant boost in throughput.
>
> I ran some tests with a gigabit ethernet adapter to get an idea of how
> this performs in comparison to using lazy iommu mode ("non-strict"):
>
> 6.6 6.6-lazy 6.6-dpu 6.6-dpu-lazy
> iperf3 recv 114 941 941 941 MBit/s
> iperf3 send 124 891 703 940 MBit/s
>
> scp recv 14.6 110 110 111 MB/s
> scp send 12.5 98.9 91.5 110 MB/s
>
> This patch in itself indeed improves things quite a bit, but there is
> still some performance that can be gained by using lazy iommu mode.
>
> Notably, lazy mode with this patch applied appears to saturate the link
> in both directions.
Maybe there is still room for SoC specific udev rules so dma masters
without firmware can be configured as "lazy", ie. like:
https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/refs/heads/main/baseboard-trogdor/chromeos-base/chromeos-bsp-baseboard-trogdor/files/98-qcom-nonstrict-iommu.rules
BR,
-R
> Tested-by: Johan Hovold <johan+linaro@kernel.org>
>
> Johan
next prev parent reply other threads:[~2023-10-31 12:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-30 23:23 [PATCH] drm/msm/dpu: Add missing safe_lut_tbl in sc8280xp catalog Bjorn Andersson
2023-10-31 8:19 ` Manivannan Sadhasivam
2023-10-31 12:46 ` Rob Clark
2023-10-31 12:35 ` Johan Hovold
2023-10-31 12:47 ` Rob Clark [this message]
2023-10-31 18:12 ` Steev Klimaszewski
2023-11-15 18:41 ` Abhinav Kumar
2023-11-21 18:40 ` Abhinav Kumar
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