Messages in this thread | | | Date | Mon, 10 Oct 2022 11:46:29 +0100 | Subject | Re: [PATCH 2/2] cpufreq: Update CPU capacity reduction in store_scaling_max_freq() | From | Lukasz Luba <> |
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+CC Daniel, since I have mentioned a few times DTPM
On 10/10/22 11:25, Peter Zijlstra wrote: > On Mon, Oct 10, 2022 at 11:12:06AM +0100, Lukasz Luba wrote: >> BTW, those Android user space max freq requests are not that long, >> mostly due to camera capturing (you can see a few in this file, >> e.g. [1]). > > It does what now ?!? Why is Android using this *at*all* ?
It tries to balance the power budget, before bad things happen randomly (throttling different devices w/o a good context what's going on). Please keep in mind that we have ~3 Watts total power budget in a phone, while several devices might be suddenly used: 1. big CPU with max power ~3-3.5 Watts (and we have 2 cores on pixel6) 2. GPU with max power ~6Watts (normally ~1-2Watts when lightly used) 3. ISP (Image Signal Processor) up to ~2Watts 4. DSP also up to 1-2Watts
We don't have currently a good mechanism which could be aware of the total power/thermal budget and relations between those devices. Vendors and OEMs run experiments on devices and profile them to work more predictable in those 'important to users' scenarios.
AFAIK Daniel Lescano is trying to help with this new interface for PowerCap: DTMP. It might be use as a new interface for those known scenarios like the camera snapshot. But that interface is on the list that I have also mentioned - it's missing the notification mechanism for the scheduler reduced capacity due to user-space new scenario.
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