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Lukasz Ziarek 2023-08-25 14:48:53 -04:00
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@ -7,9 +7,8 @@ Historically, systems have addressed the competing goals of energy and latency o
On modern systems, CPUs typically consist of multiple cores, often of different types, that run at different speeds (known as P-states) or can be turned on and off into idle (known as C-states).
A policy, or `governor', sets the CPU's frequency (P-state) when there is pending computation, optimizing performance at the expense of energy, or visa versa.
The governor runs in conjunction with other policies, in particular (i) the scheduler -- which determines what tasks are run on what CPU cores and (ii) the idle policy -- which places CPUs with no pending work into a (idle) C-state.
Hardware design on phones can constrain governor policy calculations.
For example, CPU speeds often cannot be set on individual cores but only on groups of CPUs -- a constraint stemming from the assymetric big-little CPU architecture, with 2 clusters of higher- and lower-performance CPU cores~\cite{big-little}.
For example, CPU speeds often cannot be set on individual cores but only on groups of CPUs -- a constraint stemming from the asymetric big-little CPU architecture, with 2 clusters of higher- and lower-performance CPU cores~\cite{big-little}.
% idle paper: https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=60fdaa6a74dec29a0538325b742bee4097247c6d#page=119
@ -37,7 +36,7 @@ We refer to the `speed' of the core in its idle state as $\fidle$
Many papers have studied the performance-energy trade-off of governors.
Yao et al. \cite{492493} established an ideal framework, but assume prior knowledge of all workloads.
Dynamic systems, by contrast, must somehow gague future work.
Dynamic systems, by contrast, must somehow gauge future work.
The common approach is to minimize energy usage subject to some performance constraint.
Calculating the constraint -- pending work -- takes several approaches.
The Polaris system \cite{korkmaz2018workload} tunes CPU speed to pending workloads based on userspace information.
@ -46,7 +45,7 @@ It requires knowledge of the pending amount of work and deadline target, informa
Instead of focusing on the current workload, Zhou et al. \cite{9591359} employ machine learning to predict it for a known QoS performance constraint.
Unsurprisingly, several studies have focused on the phone platform given the later's energy constraints, generally seeking to maintain user experience as the constraint.
The system proposed by Chen et al. \cite{7372574, 8356047} gagues workload on phone games by tracking CPU-GPU interaction and dynamically selects among existing governors.
The system proposed by Chen et al. \cite{7372574, 8356047} gauges workload on phone games by tracking CPU-GPU interaction and dynamically selects among existing governors.
Li et al. \cite{10.1145/3061639.3062239, 9153119} go further, predicting future work by categorizing game graphic scenes.
Broyde et al. \cite{8226044} combine scaling non-idle CPU count with CPU frequency to tune their system.
The Maestro system \cite{8410428}, like ours, recognizes that existing policies can unduly overreact, resulting in CPU overperformance.
@ -60,8 +59,9 @@ Zhisheng et al. \cite{10.1145/2973750.2973780} constrain streaming, analyzing th
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Begem et al. take the opposite of the general approach and maximize performance pursuant to energy constraints on phones.\cite{7314145}
A system that potentially constrains comptation resources needs to measure the cost.
Meeting query latencies or screendraws are common measurements used in the previous studies.
A system that potentially constrains computation resources needs to measure the cost.
Meeting query latencies or screendraws are common measurements used in previous studies.
None of these, to our knowledge, uses our approach of observing that an approximate energy-minimum setting already suffices to maintain acceptable performance targets, baring specific identifiable cases.
@ -70,7 +70,6 @@ Meeting query latencies or screendraws are common measurements used in the previ
None of these, to our knowledge, uses our approach of observing that an approximate energy-minimum setting already suffices to maintain acceptable performance targets, baring specific identifiable cases.