On Fri, 6 Jan 2023 at 19:28, Bjorn Andersson <andersson@xxxxxxxxxx> wrote: > > On Fri, Jan 06, 2023 at 05:46:18PM +0100, Vincent Guittot wrote: > > Seems like using get_maintainer.pl would have saved you some trouble ;) The worst is that I used it but only checked names and not emails when I reused the list of the original patch :-( > > > While stressing EAS on my dragonboard RB3, I have noticed that LITTLE cores > > where never selected as the most energy efficient CPU whatever the > > utilization level of waking task. > > > > energy model framework uses its cost field to estimate the energy with > > the formula: > > > > nrg = cost of the selected OPP * utilization / CPU's max capacity > > > > which ends up selecting the CPU with lowest cost / max capacity ration > > as long as the utilization fits in the OPP's capacity. > > > > If we compare the cost of a little OPP with similar capacity of a big OPP > > like : > > OPP(kHz) OPP capacity cost max capacity cost/max capacity > > LITTLE 1766400 407 351114 407 863 > > big 1056000 408 520267 1024 508 > > > > This can be interpreted as the LITTLE core consumes 70% more than big core > > for the same compute capacity. > > > > According to [1], LITTLE consumes 10% less than big core for Coremark > > benchmark at those OPPs. If we consider that everything else stays > > unchanged, the dynamic-power-coefficient of LITTLE core should be > > only 53% of the current value: 290 * 53% = 154 > > > > Set the dynamic-power-coefficient of CPU0-3 to 154 to fix the energy model. > > > > This is sounds reasonable. > > But if the math was wrong for SDM845, I would assume that sm8150 and > sm8250 are wrong as well, as that's what 0e0a8e35d725 is based on. And > should I assume that patches for other platforms are off by 53% as well? I don't think that we can assume that there is an error and in particular the same 53% error for others. > > Can you help me understand how to arrive at this number? (Without > considering everything else stays unchanged, if needed). In order to do the full computation, we need the voltage of each OPP which I don't have as they are provided by the LUT at boot IIUC. Instead I have used the debugfs output of the energy model and compared the value of (perf_state->cost/cpu_max_capacity) with the energy and duration figures available in [1]. In the case of SDM845, it was pretty easy to compare the OPPs of big and LITTLE because the duration and the perf result were the same for 2 OPPS so we should have : (little OPP(1766400)->cost / little max capacity (407)) / (big OPP(1056000)->cost / big max capacity(1024)) = little OPP(1766400) energy / big OPP(1056000) energy (little OPP(1766400)->cost / little max capacity (407)) / (big OPP(1056000)->cost / big max capacity(1024)) = 0.90 but current output gives: (little OPP(1766400)->cost / little max capacity (407)) / (big OPP(1056000)->cost / big max capacity(1024)) = 1.70 As we consider everything else constant, it can be simplified by: correct_little_dynamic-power-coefficient * const_A = 0.90 Whereas we currently have current_little_dynamic-power-coefficient * const_A = 1.70 and we ends up with correct_little_dynamic-power-coefficient = 0.90 / 1.70 * current_little_dynamic-power-coefficient = 154 That being said, it can be simpler as the energy model provide the power figures little OPP(1766400)->power = 351114 uW big OPP(1056000)->power = 195991 uW ration = 1.79 [1] results gives little OPP(1766400)->power = 193.281 mW big OPP(1056000)->power = 216.405 mW ratio = 0.89 The ratios are a bit different and give a correct_little_dynamic-power-coefficient = 144 which is different than when using ->cost. This probably comes from rounding and which figures have been used to compute the model. If you have Voltage of OPP, the formula used in energy model is power (uW) = dynamic-power-coefficient * uV^2 * Freq (Mhz) so you can compute dynamic-power-coefficient for each OPPs. They should be close and then you will have to decide which one is the "best" I don't have access to sdm8150 or sdm8250 boards but you can use the same process to check that the energy model is aligned with the figures in [1] [1] https://github.com/kdrag0n/freqbench/tree/master/results Regards, Vincent > > Regards, > Bjorn > > > [1] https://github.com/kdrag0n/freqbench/tree/master/results/sdm845/main > > > > Fixes: 0e0a8e35d725 ("arm64: dts: qcom: sdm845: correct dynamic power coefficients") > > Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> > > --- > > arch/arm64/boot/dts/qcom/sdm845.dtsi | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi > > index 65032b94b46d..869bdb9bce6e 100644 > > --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi > > +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi > > @@ -198,7 +198,7 @@ CPU0: cpu@0 { > > reg = <0x0 0x0>; > > enable-method = "psci"; > > capacity-dmips-mhz = <611>; > > - dynamic-power-coefficient = <290>; > > + dynamic-power-coefficient = <154>; > > qcom,freq-domain = <&cpufreq_hw 0>; > > operating-points-v2 = <&cpu0_opp_table>; > > interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>, > > @@ -222,7 +222,7 @@ CPU1: cpu@100 { > > reg = <0x0 0x100>; > > enable-method = "psci"; > > capacity-dmips-mhz = <611>; > > - dynamic-power-coefficient = <290>; > > + dynamic-power-coefficient = <154>; > > qcom,freq-domain = <&cpufreq_hw 0>; > > operating-points-v2 = <&cpu0_opp_table>; > > interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>, > > @@ -243,7 +243,7 @@ CPU2: cpu@200 { > > reg = <0x0 0x200>; > > enable-method = "psci"; > > capacity-dmips-mhz = <611>; > > - dynamic-power-coefficient = <290>; > > + dynamic-power-coefficient = <154>; > > qcom,freq-domain = <&cpufreq_hw 0>; > > operating-points-v2 = <&cpu0_opp_table>; > > interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>, > > @@ -264,7 +264,7 @@ CPU3: cpu@300 { > > reg = <0x0 0x300>; > > enable-method = "psci"; > > capacity-dmips-mhz = <611>; > > - dynamic-power-coefficient = <290>; > > + dynamic-power-coefficient = <154>; > > qcom,freq-domain = <&cpufreq_hw 0>; > > operating-points-v2 = <&cpu0_opp_table>; > > interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_EBI1 3>, > > -- > > 2.34.1 > >
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