Messages in this thread | | | Subject | Re: [PATCH v4 2/3] sched/fair: Take thermal pressure into account while estimating energy | From | Dietmar Eggemann <> | Date | Wed, 16 Jun 2021 19:24:36 +0200 |
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On 15/06/2021 18:09, Lukasz Luba wrote: > > On 6/15/21 4:31 PM, Dietmar Eggemann wrote: >> On 14/06/2021 21:11, Lukasz Luba wrote:
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>> It's important to highlight that this will only fix this issue between >> schedutil and EAS when it's due to `thermal pressure` (today only via >> CPU cooling). There are other places which could restrict policy->max >> via freq_qos_update_request() and EAS will be unaware of it. > > True, but for this I have some other plans.
As long as people are aware of the fact that this was developed to be beneficial for `EAS - IPA` integration, I'm fine with this.
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>> IMHO, this means that this is catered for the IPA governor then. I'm not >> sure if this would be beneficial when another thermal governor is used? > > Yes, it will be, the cpufreq_set_cur_state() is called by > thermal exported function: > thermal_cdev_update() > __thermal_cdev_update() > thermal_cdev_set_cur_state() > cdev->ops->set_cur_state(cdev, target) > > So it can be called not only by IPA. All governors call it, because > that's the default mechanism.
True, but I'm still not convinced that it is useful outside `EAS - IPA`.
>> The mechanical side of the code would allow for such benefits, I just >> don't know if their CPU cooling device + thermal zone setups would cater >> for this? > > Yes, it's possible. Even for custom vendor governors (modified clones > of IPA)
Let's stick to mainline here ;-) It's complicated enough ...
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>> Maybe shorter? >> >> struct cpumask *pd_mask = perf_domain_span(pd); >> - unsigned long cpu_cap = >> arch_scale_cpu_capacity(cpumask_first(pd_mask)); >> + int cpu = cpumask_first(pd_mask); >> + unsigned long cpu_cap = arch_scale_cpu_capacity(cpu); >> + unsigned long _cpu_cap = cpu_cap - >> arch_scale_thermal_pressure(cpu); >> unsigned long max_util = 0, sum_util = 0; >> - unsigned long _cpu_cap = cpu_cap; >> - int cpu; >> - >> - _cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask)); > > Could be, but still, the definitions should be sorted from longest on > top, to shortest at the bottom. I wanted to avoid modifying too many > lines with this simple patch.
Only if there are no dependencies, but here we have already `cpu_cap -> pd_mask`. OK, not a big deal.
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>> There is IPA specific code in cpufreq_set_cur_state() -> >> get_state_freq() which accesses the EM: >> >> ... >> return cpufreq_cdev->em->table[idx].frequency; >> ... >> >> Has it been discussed that the `per-PD max (allowed) CPU capacity` (1) >> could be stored in the EM from there so that code like the EAS wakeup >> code (compute_energy()) could retrieve this information from the EM? > > No, we haven't think about this approach in these patch sets. > The EM structure given to the cpufreq_cooling device and stored in: > cpufreq_cdev->em should not be modified. There are a few places which > receive the EM, but they all should not touch it. For those clients > it's a read-only data structure. > >> And there wouldn't be any need to pass (1) into the EM (like now via >> em_cpu_energy()). >> This would be signalling within the EM compared to external signalling >> via `CPU cooling -> thermal pressure <- EAS wakeup -> EM`. > > I see what you mean, but this might cause some issues in the design > (per-cpu scmi cpu perf control). Let's use this EM pointer gently ;)
OK, with the requirement that clients see the EM as ro:
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
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