Re: [PATCH 2/3] PM: EM: Make em_cpu_energy() able to return bigger values
From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Date: 2021-07-05 12:45:12
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lkml
On 25/06/2021 17:26, Lukasz Luba wrote:
The Energy Model (EM) em_cpu_energy() is responsible for providing good estimation regarding CPUs energy. It contains proper data structures which are then used during calculation. The values stored in there are in milli-Watts precision (or in abstract scale) smaller that 0xffff, which use
I guess you refer to 'if (... || power > EM_MAX_POWER)' check in em_create_perf_table() [kernel/power/energy_model.c].
sufficient unsigned long even on 32-bit machines. There are scenarios where
^^^^^^^^^ Can you describe these scenarios better with one example (EAS placement of an example task on a 2 PD system) which highlights the issue and how it this patch-set solves it? In this example you can list all the things which must be there to create a situation in EAS in which the patch-set helps.
we would like to provide calculated estimations in a better precision and the values might be 1000 times bigger. This patch makes possible to use
Where is this `1000` coming from?
quoted hunk ↗ jump to hunk
quite big values for also 32-bit machines. Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> --- include/linux/energy_model.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h index 3f221dbf5f95..2016f5a706e0 100644 --- a/include/linux/energy_model.h +++ b/include/linux/energy_model.h@@ -101,7 +101,7 @@ void em_dev_unregister_perf_domain(struct device *dev); * Return: the sum of the energy consumed by the CPUs of the domain assuming * a capacity state satisfying the max utilization of the domain. */ -static inline unsigned long em_cpu_energy(struct em_perf_domain *pd, +static inline u64 em_cpu_energy(struct em_perf_domain *pd, unsigned long max_util, unsigned long sum_util, unsigned long allowed_cpu_cap) {@@ -180,7 +180,7 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd, * pd_nrg = ------------------------ (4) * scale_cpu */ - return ps->cost * sum_util / scale_cpu; + return div_u64((u64)ps->cost * sum_util, scale_cpu); } /**@@ -217,7 +217,7 @@ static inline struct em_perf_domain *em_pd_get(struct device *dev) { return NULL; } -static inline unsigned long em_cpu_energy(struct em_perf_domain *pd, +static inline u64 em_cpu_energy(struct em_perf_domain *pd, unsigned long max_util, unsigned long sum_util, unsigned long allowed_cpu_cap) {