Messages in this thread |  | | Date | Thu, 4 Jan 2024 16:56:30 +0000 | | Subject | Re: [PATCH v5 15/23] PM: EM: Optimize em_cpu_energy() and remove division | | From | Lukasz Luba <> |
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On 1/4/24 16:30, Dietmar Eggemann wrote: > On 20/12/2023 09:42, Lukasz Luba wrote: >> >> >> On 12/12/23 18:50, Dietmar Eggemann wrote: >>> On 29/11/2023 12:08, Lukasz Luba wrote: > > [...] > >>>> With this optimization, the em_cpu_energy() should run faster on the Big >>>> CPU by 1.43x and on the Little CPU by 1.69x. >>> >>> Where are those precise numbers are coming from? Which platform was it? >> >> That was mainline big.Little board rockpi4 b w/ rockchip 3399, present > > IMHO, you should mention the platform here so people don't wonder. > >> quite a few commercial devices (e.g. chromebooks or plenty other seen in >> DT). The numbers are from measuring the time it takes to run this >> function em_cpu_cost() in a loop for mln of times. Thus, the instruction >> cache and data cache should be hot, but the operation would impact the >> different score. > > [...] > >>> Can you not keep the existing comment and only change: >>> >>> (a) that ps->cap id ps->performance in (2) and >>> >>> (b) that: >>> >>> * ps->power * cpu_max_freq cpu_util >>> * cpu_nrg = ------------------------ * --------- (3) >>> * ps->freq scale_cpu >>> >>> <---- (old) ps->cost ---> >>> >>> is now >>> >>> ps->power * cpu_max_freq 1 >>> ps-> cost = ------------------------ * ---------- >>> ps->freq scale_cpu >>> >>> <---- (old) ps->cost ---> >>> >>> and (c) that (4) has changed to: >>> >>> * pd_nrg = ps->cost * \Sum cpu_util (4) >>> >>> which avoid the division? >>> >>> Less changes is always much nicer since it makes it so much easier to >>> detect history and review changes. >> >> I'm open to change that, but I will have to contact you offline >> what you mean. This comment section in code is really tricky to >> handle right. > > OK, the changes you showed me offline LGTM. > > [...] >
All good then. Thank you for the comments. I'll send v6.
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