2.1.12 Power and performance management
Power10 processor-based servers implement an enhanced version of the power management EnergyScale technology. As in the previous POWER9 EngeryScale implementation, the Power10 EnergyScale technology supports dynamic processor frequency changes that are dependent on several factors, such as workload characteristics, the number of active cores, and environmental conditions.
Based on the extensive experience that was gained over the past few years, the Power10 EnergyScale technology evolved to use the following effective and simplified set of operational modes:
Ê Power saving mode
Ê Static mode (nominal frequency)
Ê Maximum performance mode (MPM)
The POWER9 dynamic performance mode (DPM) has many features in common with the POWER9 maximum performance mode (MPM). Because of this redundant nature of characteristics, the DPM for Power10 processor-based systems was removed in favor of an enhanced MPM. For example, the maximum frequency is now achieveable in the Power10 enhanced maximum performance mode (regardless of the number of active cores), which was not always the case with POWER9 processor-based servers.
The Power10 processor-based Power E1080 system features MPM enabled by default. This mode dynamically adjusts processor frequency to maximize performance and enable a much higher processor frequency range. Each of the power saver modes deliver consistent system performance without any variation if the nominal operating environment limits are met.
For Power10 processor-based systems that are under control of the PowerVM hypervisor, the MPM is a system-wide configuration setting, but each processor module frequency is optimized separately.
The following factors determine the maximum frequency that a processor module can run at:
Ê Processor utilization: Lighter workloads run at higher frequencies.
Ê Number of active cores: Fewer active cores run at higher frequencies.
Ê Environmental conditions: At lower ambient temperatures, cores are enabled to run at higher frequencies.
The following Power10 EnergyScale modes are available:
Ê Power saving mode
The frequency is set to the minimum frequency to reduce energy consumption. Enabling this feature reduces power consumption by lowering the processor clock frequency and voltage to fixed values. This configuration reduces power consumption of the system while delivering predictable performance.
Ê Static mode
The frequency is set to a fixed point that can be maintained with all normal workloads and in all normal environmental conditions. This frequency is also referred to as nominal frequency.
Ê Maximum performance mode
Workloads run at the highest frequency possible, depending on workload, active core count, and environmental conditions. The frequency does not go below the static frequency for all normal workloads and in all normal environmental conditions.
66 IBM Power E1080: Technical Overview and Introduction
In MPM, the workload is run at the highest frequency possible. The higher power draw enables the processor modules to run in an MPM typical frequency range (MTFR), where the lower limit is well above the nominal frequency and the upper limit is given by the system’s maximum frequency.
The MTFR is published as part of the system specifications of a specific Power10 system if it is running by default in MPM. The higher power draw potentially increases the fan speed of the respective system node to meet the higher cooling requirements, which in turn causes a higher noise emission level of up to 15 decibels.
The processor frequency typically stays within the limits that are set by the MTFR, but can be lowered to frequencies between the MTFR lower limit and the nominal frequency at high ambient temperatures above 27 °C (80.6 °F). If the data center ambient environment is less than 27 °C, the frequency in MPM consistently is in the upper range of the MTFR (roughly 10% – 20% better than nominal). At lower ambient temperatures (below 27 °C, or 80.6 °F), MPM mode also provides deterministic performance. As the ambient temperature increases above 27 °C, determinism can no longer be ensured. This mode is the default mode in the Power E1080.
Ê Idle power saver mode (IPS)
IPS mode lowers the frequency to the minimum if the entire system (all cores of all sockets) is idle. It can be enabled or disabled separately from all other modes. The Power E1080 does not support this mode.
Figure 2-8 shows the comparative frequency ranges for the Power10 power saving mode, static or nominal mode, and the maximum performance mode. The frequency adjustments for different workload characteristics, ambient conditions, and idle states are also indicated.
Figure 2-8 Power10 power management modes and related frequency ranges
Chapter 2. Architecture and technical overview 67
Table 2-4 shows the power saving mode and the static mode frequencies, and the frequency ranges of the MPM for all three processor module types that are available for the Power E1080 server.
Table 2-4 Characteristic frequencies and frequency ranges for Power E1080 server
For Power E1080 servers, the MPM is enabled by default.
The controls for all power saver modes are available on the Advanced System Management Interface (ASMI) and can be dynamically modified. A system administrator can also use the Hardware Management Console (HMC) to set power saver mode or to enable static mode or MPM.
Figure 2-9 shows the ASM interface menu for Power and Performance Mode Setup on a Power E1080 server.
Figure 2-9 Power E1080 ASMI menu for Power and Performance Mode setup
68 IBM Power E1080: Technical Overview and Introduction
Figure 2-10 shows the HMC menu for power and performance mode setup.
Figure 2-10 Power E1080 HMC menu for Power and Performance Mode setup