Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 5 Jun 2014 10:49:35 +0200 | Subject | Re: [RFC PATCH 01/16] sched: Documentation for scheduler energy cost model |
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Hi Morten,
On 23 May 2014 20:16, Morten Rasmussen <morten.rasmussen@arm.com> wrote: > This documentation patch provide a brief overview of the experimental > scheduler energy costing model and associated data structures. > > Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> > --- > Documentation/scheduler/sched-energy.txt | 66 ++++++++++++++++++++++++++++++ > 1 file changed, 66 insertions(+) > create mode 100644 Documentation/scheduler/sched-energy.txt > > diff --git a/Documentation/scheduler/sched-energy.txt b/Documentation/scheduler/sched-energy.txt > new file mode 100644 > index 0000000..c6896c0 > --- /dev/null > +++ b/Documentation/scheduler/sched-energy.txt > @@ -0,0 +1,66 @@ > +Energy cost model for energy-aware scheduling (EXPERIMENTAL) > + > +Introduction > +============= > +The basic energy model uses platform energy data stored in sched_energy data > +structures attached to the sched_groups in the sched_domain hierarchy. The > +energy cost model offers two function that can be used to guide scheduling > +decisions: > + > +1. energy_diff_util(cpu, util, wakeups)
Could you give us mor edetails of what util and wakeups are ? util is a absolute value or a delta Is wakeups a boolean or does wakeups define a number of tasks/cpus that wake up ?
> +2. energy_diff_task(cpu, task) > + > +Both return the energy cost delta caused by adding/removing utilization or a > +task to/from a specific cpu. > + > +CONFIG_SCHED_ENERGY needs to be defined in Kconfig to enable the energy cost > +model and associated data structures. > + > +The basic algorithm > +==================== > +The basic idea is to determine the energy cost at each level in sched_domain > +hierarchy based on utilization: > + > + for_each_domain(cpu, sd) { > + sg = sched_group_of(cpu) > + energy_before = curr_util(sg) * busy_power(sg) > + + 1-curr_util(sg) * idle_power(sg) > + energy_after = new_util(sg) * busy_power(sg) > + + 1-new_util(sg) * idle_power(sg) > + + new_util(sg) * task_wakeups > + * wakeup_energy(sg) > + energy_diff += energy_before - energy_after > + } > + > + return energy_diff
So this is the algorithm used in energy_diff_util and energy_diff_task ?
it's not straight foward for me to map the algorithm variable and the function argument
> + > +Platform energy data > +===================== > +struct sched_energy has the following members: > + > +cap_states: > + List of struct capacity_state representing the supported capacity states > + (P-states). struct capacity_state has two members: cap and power, which > + represents the compute capacity and the busy power of the state. The > + list must ordered by capacity low->high. > + > +nr_cap_states: > + Number of capacity states in cap_states. > + > +max_capacity: > + The highest capacity supported by any of the capacity states in > + cap_states.
can't you directly use cap_states[nr_cap_states].cap has the array is ordered ?
Vincent > + > +idle_power: > + Idle power consumption. Will be extended to support multiple C-states > + later. > + > +wakeup_energy: > + Energy cost of wakeup/power-down cycle for the sched_group which this is > + attached to. Will be extended to support different costs for different > + C-states later. > + > +There are no unit requirements for the energy cost data. Data can be normalized > +with any reference, however, the normalization must be consistent across all > +energy cost data. That is, one bogo-joule/watt must be same quantity for data, > +but we don't care what it is. > -- > 1.7.9.5 > >
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