linux-kernel - Re: [PATCH] soc: qcom: icc-bwmon: Update zone1_thres

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Date: Wed, 22 May 2024 11:19:42 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Shivnandan Kumar <quic_kshivnan@...cinc.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 quic_rgottimu@...cinc.com
Subject: Re: [PATCH] soc: qcom: icc-bwmon: Update zone1_thres_count to 3

On 22/05/2024 11:05, Shivnandan Kumar wrote:
> 
> 
> On 5/22/2024 1:58 PM, Krzysztof Kozlowski wrote:
>> On 22/05/2024 10:15, Shivnandan Kumar wrote:
>>> Update zone1_thres_count to 3 from 16 so that
>>> driver can reduce bus vote in 3 sample windows instead
>>> of waiting for 16 windows. This is in line with downstream
>>> implementation.
>>>
>>
>> This might make bwmon quite jittery. I don't think downstream is the
>> source of truth here. Please provide some measurements *on mainline tree*.
>>
> 
> Hi Krzysztof,
> 
> The 16-window (64 ms) waiting time is too long to reduce the bus vote.
> At higher FPS, there will be multiple frames in 64ms e.g. 4 frames at 
> 60FPS in 64ms. Hence, delay of 64ms in decision making will lead to 
> higher power regression. I’ve tested this change for 4K video playback 
> on mainline tree, and there’s a significant power-saving.

Please include it, with measurement below, in the commit msg.

> I propose to make it a tunable,so that user space can tune it
> based on runtime depending on fps.>
> USECASE                     zone1_thres_count=16     zone1_thres_count=3
> 4K video playback           236.15 mA	             203.15 mA
> 
> Thanks,
> Shivnandan
> 
>> Best regards,
>> Krzysztof
>>

Best regards,
Krzysztof