Alexandre Peixoto Ferreira’s research while affiliated with IBM and other places

In the modern multi-tenant cloud, resource sharing increases utilization but causes performance interference between tenants. More generally, performance isolation is also relevant in any multi-workload scenario involving shared resources. Last level cache (LLC) on processors is shared by all CPU cores in x86, thus the cloud tenants inevitably suffer from the cache flush by their noisy neighbors running on the same socket. Intel Cache Allocation Technology (CAT) provides a mechanism to assign cache ways to cores to enable cache isolation, but its static configuration can result in underutilized cache when a workload cannot benefit from its allocated cache capacity, and/or lead to sub-optimal performance for workloads that do not have enough assigned capacity to fit their working set. In this work, we propose a new dynamic cache management technology (dCat) to provide strong cache isolation with better performance. For each workload, we target a consistent, minimum performance bound irrespective of others on the socket and dependent only on its rightful share of the LLC capacity. In addition, when there is spare capacity on the socket, or when some workloads are not obtaining beneficial performance from their cache allocation, dCat dynamically reallocates cache space to cache-intensive workloads. We have implemented dCat in Linux on top of CAT to dynamically adjust cache mappings. dCat requires no modifications to applications so that it can be applied to all cloud workloads. Based on our evaluation, we see an average of 25% improvement over shared cache and 15.7% over static CAT for selected, memory intensive, SPEC CPU2006 workloads. For typical cloud workloads, with Redis we see 57.6% improvement (over shared LLC) and 26.6% improvement (over static partition) and with ElasticSearch we see 11.9% improvement over both.

A method, system, and computer program product for relating a data processing system with a power branch circuit are provided in the illustrative embodiments. Each signal in a set of signals is combined with a power signal to form a set of combination signals, the power signal including a first power usage by the data processing system and a second power usage by a modulating signal. An amplitude of a corresponding signal in each combined signal in the set of combined signals is determined over a period. Using a discriminating logic, a determination is made whether the modulating signal is present in the power signal. Responsive to the discriminating logic producing an affirmative result, the data processing system is related with the power branch circuit.

A flexible current and voltage sensor provides ease of installation of a current sensor, and optionally a voltage sensor in application such as AC branch circuit wire measurements, which may require installation in dense wiring conditions and/or in live panels where insulating gloves must be worn. The sensor includes at least one flexible ferromagnetic strip that is affixed to a current sensing device at a first end. The second end is secured to the other side of the current sensing device or to another flexible ferromagnetic strip extending from the other side of the current sensing device to form a loop providing a closed pathway for magnetic flux. A voltage sensor may be provided by metal foil affixed to the inside of the flexible ferromagnetic strip. A clamp body, which can be a spring loaded handle operated clamp or a locking fastener, can secure the ferromagnetic strip around the wire.

A detachable current sensor provides an isolated and convenient device to measure current passing through a cable such as an AC power cable or non-metallic (NM) sheathed cable. Information about the magnitude and or phases of the currents passing through and/or voltages on the conductors is obtained by measuring the magnetic field at multiple circumferential positions around the cable using multiple semiconductor magnetic field sensors. A processing subsystem coupled to the multiple semiconductor magnetic field sensors determines information about the currents flowing in the conductors of the cable, including the current magnitude(s), and/or the phases and number of phases present in the cable, which can form part of a power measurement system that is used for energy monitoring, and/or for control purposes.

A mechanism is provided for dynamically changing power caps for a set of powered elements. Current being consumed by the set of powered elements P on a branch circuit is measured and available current on the branch circuit is determined. A new total power cap for a current time period t is identified based on a current total power cap and the measured current. A difference in total power caps (ΔTPC) is determined and, for each powered element p in the set of powered elements P at the current time period, a new power cap PC (p,t) is determined based on the previous power cap PC(p,t−1) and the difference of the total power caps to the set of powered elements P. A power cap of each powered element p is then dynamically set to the new power cap PC (p,t).

A method for relating a data processing system with a power branch circuit is provided in the illustrative embodiments. A second signal is combined with a power signal to form a combination signal, the power signal including a first power usage by the data processing system and a second power usage by a modulating signal. The second signal is synchronized with the modulating signal in the power signal. A determination is made whether an amplitude of a frequency of the second signal is increasing in the combined signal over a period. Responsive to the determining being affirmative, the data processing system is related with the power branch circuit.

Calibration of a non-contact current sensor provides improved accuracy for measuring current conducted through a conductor such as an AC branch circuit wire. In a calibration mode, a predetermined DC current is injected through a conductor integrated in the non-contact current sensor. The magnitude of the magnetic field is measured using a sensing element of the non-contact current sensor. Then, when operating in measurement mode, a current conducted in a wire passing through the non-contact current sensor is determined by correcting the output of the non-contact current sensor using the result of the measurement made in the calibration mode.

Calibration of a non-contact voltage sensor provides improved accuracy for measuring voltage on a conductor such as an AC branch circuit wire. In a calibration mode, a predetermined voltage is imposed on a first voltage sensing conductor integrated in the non-contact voltage sensor, while a voltage on a second voltage sensing conductor is measured using a circuit of predetermined input impedance. The capacitance between the wire and each of the voltage sensing conductors may be the same, so that in measurement mode, when the first and second voltage sensing conductors are coupled together, the effective series capacitance provided in combination with the predetermined input impedance is four times as great. The results of the voltage measurement made in the calibration mode can thereby be used to adjust subsequent voltage measurements made in measurement mode with the first and second voltage sensing conductors combined in parallel.

This demonstration presents a power panel level power monitoring and management (PMM) system developed at IBM Research. The ultimate goal of this project is to develop a low-cost, high accuracy, non-intrusive and retrofittable data center power management system.