Re: [PATCH v3] soc: qcom: icc-bwmon: Update zone1_thres_count to 3

[Pushpendra Singh]

On 3/17/2026 9:06 PM, Dmitry Baryshkov wrote:
> On Tue, Mar 17, 2026 at 11:15:51AM +0530, Pushpendra Singh wrote:
>>
>> On 2/28/2026 3:19 PM, Krzysztof Kozlowski wrote:
>>> On 27/02/2026 12:10, Pushpendra Singh wrote:
>>>> From: Shivnandan Kumar <quic_kshivnan@xxxxxxxxxxx>
>>>>
>>>> Reduce zone1_thres_count from 16 to 3 so the driver can lower the bus
>>>> vote after 3 sample windows instead of waiting for 16. The previous
>>>> 16‑window delay (~64 ms) is too long at higher FPS workloads,
>>>> causing delayed decision making and measurable power regression.
>>>>
>>>> Empirical tuning showed that lower values (e.g., 2) made bwmon behavior
>>>> jittery, while higher values (4–6) were stable but less responsive and
>>>> reduced power savings. A value of 3 provided the best balance: responsive
>>>> enough for timely power reduction while maintaining stable bwmon
>>>> operation.
>>>>
>>>> Significant power savings were observed across multiple use cases when
>>>> reducing the threshold from 16 to 3:
>>>>
>>>> USECASE			zone1_thres_count=16     zone1_thres_count=3
>>>> 4K video playback	   236.15 mA                  203.15 mA
>>>> Sleep			    7mA			        6.9mA
>>>> Display (idle display)	  71.95mA			67.11mA
>>> Which hardware exactly? Which kernel?
>>>
>>> You keep running this on downstream, like a lot of code from Qualcomm
>>> and speeches on conferences, so I just don't trust the numbers.
>>
>> The numbers presented were obtained on then upstream 6.6 based kernels across multiple SoCs (sc7280/sa8775p).
> 
> Please don't use old kernels for upstream work.

Thanks for the feedback, and apologies for the delay. We validated power and performance workloads using the v7.3-rc5 kernel on the branch below, comparing zone1_thres_count=16 with zone1_thres_count=3.
Branch : https://github.com/abelvesa/linux.git

Usecase                                 zone1_cnt=16	zone1_cnt=3	saving           
Youtube streaming on browser(power)	4126.49mW	3991.30mW	3.28%
Google meet audio(power)		3058.79mw	2929.73mW	4.22%
Speedometer3.1(performance)		25.8		26.5		+2.7%
GBv6.5 ST(performance)			3907		3905		-0.1%
GBv6.5 MT(performance)			18636		18680		+0.2%

Based on these measurements, zone1_thres_count=3 provides a measurable SoC power benefit for the tested use cases, while no meaningful performance regression was observed.

Thanks,
Pushpendra