linux-kernel - Re: [PATCH] drm/lima: add governor data with pre-defined thresholds

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Date:   Wed, 27 Jan 2021 11:11:14 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Christian Hewitt <christianshewitt@...il.com>
Cc:     Qiang Yu <yuq825@...il.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, lima@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, Steven Price <steven.price@....com>
Subject: Re: [PATCH] drm/lima: add governor data with pre-defined thresholds



On 1/27/21 10:24 AM, Lukasz Luba wrote:
> Hi Christian,
> 
> On 1/25/21 8:18 AM, Christian Hewitt wrote:
>> This patch adapts the panfrost pre-defined thresholds change [0] to the
>> lima driver to improve real-world performance. The upthreshold value has
>> been set to ramp GPU frequency to max freq faster (compared to panfrost)
>> to compensate for the lower overall performance of utgard devices.
>>
>> [0] 
>> https://patchwork.kernel.org/project/dri-devel/patch/20210121170445.19761-1-lukasz.luba@arm.com/ 
>>
>>
>> Signed-off-by: Christian Hewitt <christianshewitt@...il.com>
>> ---
>> I have been using Kodi as my test application. If you scroll in library
>> views with hundreds of list items and the panfrost values the slow GPU
>> ramp up is quite noticeable and the GUI feels sluggish. As everything
>> lima runs on is inherently slower than panfrost using devices I believe
>> it's better to ramp up to max freq quicker.
> 
> It's quite low value for the upthreshold, but I believe you have
> experimented and observed that a bit higher (30, 40?) don't work well.
> I don't know the Kodi system, though.
> 
> You can check if the other frequencies are also used in statistics for
> devfreq device:
> cat /sys/class/devfreq/<your_gpu>/trans_stats
> 
> If they are also used, then it OK (better than stuck at min freq).

I've just realized that your board might suffer a another issue.
Please apply this patch [1] and run your experiments with upthresholds.


[1] https://lore.kernel.org/lkml/20210127105121.20345-1-lukasz.luba@arm.com/