Messages in this thread | | | Date | Mon, 26 Jun 2023 08:45:40 +0100 | Subject | Re: [PATCH V4] thermal/core/power_allocator: reset thermal governor when trip point is changed | From | Lukasz Luba <> |
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On 6/25/23 09:39, Di Shen wrote: > On Fri, Jun 23, 2023 at 4:10 PM Lukasz Luba <lukasz.luba@arm.com> wrote: >> >> >> >> On 6/22/23 19:27, Rafael J. Wysocki wrote:
[snip]
>>> >>> So there seems to be a claim that IPA is the only governor needing the >>> ->reset() callback, but I have not seen any solid analysis confirming >>> that. It very well may be the case, but then the changelog should >>> clearly explain why this is the case IMO. >> >> I agree, the patch header doesn't explain that properly. Here is the >> explanation for this Intelligent Power Allocator (IPA): >> >> The IPA controls temperature using PID mechanism. It's a closed >> feedback loop. That algorithm can 'learn' from the 'observed' >> in the past reaction for it's control decisions and accumulates that >> information in the part called 'error integral'. Those accumulated >> 'error' gaps are the differences between the set target value and the >> actually achieved value. In our case the target value is the target >> temperature which is coming from the trip point. That part is then used >> with the 'I' (of PID) component, so we can compensate for those >> 'learned' mistakes. >> Now, when you change the target temperature value - all your previous >> learned errors won't help you. That's why Intelligent Power Allocator >> should reset previously accumulated history. >> > > Yes, THAT's the point! > Maybe I need to write the commit message in more detail. >
Yes, please extend that description.
Regards, Lukasz
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