ARM’s big LITTLE Technology:
Most embedded systems vie for saving the power and for this purpose a lot of efforts are needed and technology need to be used. So ARM processors are very widely being used in mobile devices nowadays.
ARM stands for Advanced RISC Machine.
RISC stands for Reduced Instruction Set Computing.
A characteristic feature of ARM processors is their low electric power consumption, which makes them particularly suitable for use in portable devices. In fact, almost all modern mobile phones and personal digital assistants contain ARM CPUs, making them the most widely used 32-bit microprocessor family in the world. Today ARMs account for over 75% of all 32-bit embedded CPUs.
ARM offers several microprocessor core designs which are used in such applications as smartphones and tablets.
Cores for 32-bit architectures include Cortex-A15, Cortex-A12, Cortex-A17, Cortex-A9, Cortex-A8, Cortex-A7 and Cortex-A5, and older "Classic ARM Processors", as well as variant architectures for microcontrollers that include these cores: ARM Cortex-R7, ARM Cortex-R5, ARM Cortex-R4, ARM Cortex-M4, ARM Cortex-M3, ARM Cortex-M1, ARM Cortex-M0+, and ARM Cortex-M0.
The latest technology introduced by ARM is the big LITTLE technology.
ARM® big.LITTLE™ processing is a power-optimization technology where high-performance ARM CPU cores are combined with the most efficient ARM CPU cores to deliver peak-performance capacity, higher sustained performance, and increased parallel processing performance, at significantly lower average power. The latest big.LITTLE software and platforms can save 75% of CPU energy in low to moderate performance scenarios, and can increase performance by 40% in highly threaded workloads. The underlying big.LITTLE software, big.LITTLE MP, automatically and seamlessly moves workloads to the appropriate CPU core based on performance needs. ARM big.LITTLE technology enables mobile SoCs to be designed for new levels of peak performance, in the same all-day battery life users expect.
Background
The performance demanded by smartphones and tablets is increasing at a much faster rate than technology improvements in battery capacity and the advances in semiconductor process nodes. The need for higher performance directly conflicts with the desire for longer battery life. The solution to this lies beyond process technology and traditional power management and requires further innovation in mobile SoC design. big.LITTLE is one of many power management technologies employed by ARM to save power in mobile SoCs. It works in tandem with Dynamic Voltage and Frequency Scaling (DVFS), clock gating, power gating, retention modes, and thermal management to deliver a full set of power control for the SoC.
big.LITTLE technology takes advantage of the dynamic usage pattern for smartphones and tablets. Periods of high processing intensity tasks such as initial web page rendering and game physics calculation alternate with typically longer periods of low processing intensity tasks such as scrolling or reading a web page, waiting for user input in a game, and lighter weight tasks like texting, e-mail and audio. The graph below (Fig.1) shows the CPU residency at various DVFS frequency states in a big.LITTLESoC, with all the relevant power management techniques in operation. It shows the usage of the big CPU cores in burst mode (i.e. for short durations at peak frequency) while the majority of runtime is managed by LITTLE cores at moderate operating frequencies.
Innovative power-saving techniques are required to sustain the pace of innovation in mobile through performance increases in the same power footprint. Many of the mobile use cases exhibit behavior like that shown in the graph above, presenting an ideal opportunity for big.LITTLE technology to save power while also delivering peak-performance in modern mobile devices.
big.LITTLE Processing – How does it work?
The high performance and high efficiency CPU clusters are connected through a cache coherent interconnect fabric such as the ARM CoreLink™ CCI-400.This hardware coherency enables the same view of the memory to both the big and LITTLE CPU clusters. The processors look like one multicore CPU to the operating system (OS). User space software on a big.LITTLESoC is identical to the software that would run on a standard Symmetrical Multi-Processing (SMP) CPU.
How does the work get scheduled to the right processor?
Global Task Scheduling (GTS) gives the OS awareness of the big and LITTLE processors, and the ability to schedule individual threads of execution on the appropriate CPU core based on dynamic run-time behavior. ARM has developed a kernel space patch set based on GTS called big.LITTLE MP that keeps track of load history as each thread runs, and uses the history to anticipate the performance needs of the thread next time it runs.
Hardware Requirements
For a big.LITTLE system to work seamlessly with software, the CPU subsystem must be fully cache coherent, and the big and LITTLE CPU cores must be fully architecturally identical; they must run all the same instructions and support the same extensions such as virtualization, large physical addressing and so on.
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Article By,
G MUKESH,
ECE DEPARTMENT,
SPHOORTHY ENGINEERING COLLEGE
Most embedded systems vie for saving the power and for this purpose a lot of efforts are needed and technology need to be used. So ARM processors are very widely being used in mobile devices nowadays.
ARM stands for Advanced RISC Machine.
RISC stands for Reduced Instruction Set Computing.
A characteristic feature of ARM processors is their low electric power consumption, which makes them particularly suitable for use in portable devices. In fact, almost all modern mobile phones and personal digital assistants contain ARM CPUs, making them the most widely used 32-bit microprocessor family in the world. Today ARMs account for over 75% of all 32-bit embedded CPUs.
ARM offers several microprocessor core designs which are used in such applications as smartphones and tablets.
Cores for 32-bit architectures include Cortex-A15, Cortex-A12, Cortex-A17, Cortex-A9, Cortex-A8, Cortex-A7 and Cortex-A5, and older "Classic ARM Processors", as well as variant architectures for microcontrollers that include these cores: ARM Cortex-R7, ARM Cortex-R5, ARM Cortex-R4, ARM Cortex-M4, ARM Cortex-M3, ARM Cortex-M1, ARM Cortex-M0+, and ARM Cortex-M0.
The latest technology introduced by ARM is the big LITTLE technology.
ARM® big.LITTLE™ processing is a power-optimization technology where high-performance ARM CPU cores are combined with the most efficient ARM CPU cores to deliver peak-performance capacity, higher sustained performance, and increased parallel processing performance, at significantly lower average power. The latest big.LITTLE software and platforms can save 75% of CPU energy in low to moderate performance scenarios, and can increase performance by 40% in highly threaded workloads. The underlying big.LITTLE software, big.LITTLE MP, automatically and seamlessly moves workloads to the appropriate CPU core based on performance needs. ARM big.LITTLE technology enables mobile SoCs to be designed for new levels of peak performance, in the same all-day battery life users expect.
Background
The performance demanded by smartphones and tablets is increasing at a much faster rate than technology improvements in battery capacity and the advances in semiconductor process nodes. The need for higher performance directly conflicts with the desire for longer battery life. The solution to this lies beyond process technology and traditional power management and requires further innovation in mobile SoC design. big.LITTLE is one of many power management technologies employed by ARM to save power in mobile SoCs. It works in tandem with Dynamic Voltage and Frequency Scaling (DVFS), clock gating, power gating, retention modes, and thermal management to deliver a full set of power control for the SoC.
big.LITTLE technology takes advantage of the dynamic usage pattern for smartphones and tablets. Periods of high processing intensity tasks such as initial web page rendering and game physics calculation alternate with typically longer periods of low processing intensity tasks such as scrolling or reading a web page, waiting for user input in a game, and lighter weight tasks like texting, e-mail and audio. The graph below (Fig.1) shows the CPU residency at various DVFS frequency states in a big.LITTLESoC, with all the relevant power management techniques in operation. It shows the usage of the big CPU cores in burst mode (i.e. for short durations at peak frequency) while the majority of runtime is managed by LITTLE cores at moderate operating frequencies.
Innovative power-saving techniques are required to sustain the pace of innovation in mobile through performance increases in the same power footprint. Many of the mobile use cases exhibit behavior like that shown in the graph above, presenting an ideal opportunity for big.LITTLE technology to save power while also delivering peak-performance in modern mobile devices.
big.LITTLE Processing – How does it work?
The high performance and high efficiency CPU clusters are connected through a cache coherent interconnect fabric such as the ARM CoreLink™ CCI-400.This hardware coherency enables the same view of the memory to both the big and LITTLE CPU clusters. The processors look like one multicore CPU to the operating system (OS). User space software on a big.LITTLESoC is identical to the software that would run on a standard Symmetrical Multi-Processing (SMP) CPU.
How does the work get scheduled to the right processor?
Global Task Scheduling (GTS) gives the OS awareness of the big and LITTLE processors, and the ability to schedule individual threads of execution on the appropriate CPU core based on dynamic run-time behavior. ARM has developed a kernel space patch set based on GTS called big.LITTLE MP that keeps track of load history as each thread runs, and uses the history to anticipate the performance needs of the thread next time it runs.
Hardware Requirements
For a big.LITTLE system to work seamlessly with software, the CPU subsystem must be fully cache coherent, and the big and LITTLE CPU cores must be fully architecturally identical; they must run all the same instructions and support the same extensions such as virtualization, large physical addressing and so on.
----------------------------------------------------------------
Article By,
G MUKESH,
ECE DEPARTMENT,
SPHOORTHY ENGINEERING COLLEGE
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| Sphoorthy Engineering College |
