Q2.12: Emulation of Asymmetrically Performing CPUs

67 %
33 %
Information about Q2.12: Emulation of Asymmetrically Performing CPUs

Published on March 20, 2014

Author: linaroorg

Source: slideshare.net


Resource: Q2.12
Name: Emulation of Asymmetrically Performing CPUs
Date: 30-05-2012
Speaker: Rob Lee

Emulation of Asymmetrically Performing CPUs Linaro Connect Q2.2012

Asymmetric CPU Performance? ● ARM's new big.LITTLE architecture is an asymmetric multiprocessor system in which two types of cores (which use the same instruction set). ○ Higher Performance cores (Cortex A15) Best performance ○ More Power Efficient cores (Cortex A7) ■ Best power efficiency, lower performance ● Similar asymmetric systems are also possible by varying the manufacturing processes of identical cores.

Emulation of Asymmetric CPU Performance? ● Linux scheduler is work is underway to allow intelligent scheduling for these type of asymmetrical CPU systems and so testing of these changes is needed. ● Actual hardware with this cpu configuration isn't (readily) available. ● The performance differences that exists on these asymmetric cpu systems can be emulated which can hopefully provide a test platform for some the scheduler work.

Host System Types for Running Emulation 1. Multicore systems whose cpu frequencies are coupled. a. Cortex-A9 2. Multicore systems whose cpu frequencies are independent from each other a. modern X86, etc. b. If in doubt, check /sys/devices/system/cpu/cpu0/cpufreq/affected_cpus .

Emulation Methods 1. Cycle Stealer - Steal the user programmed percentage of cpu processing cycles in order to degrade performance. 2. Frequency limiting- For systems whose cpu frequencies are not couples, limit the frequency of chosen cpus to degrade performance.

Cycle Stealer Pros and Cons Pros: ● Can be run on any multicore system Cons: ● Subject to the overhead and accuracy of the implementation. ● Current Implementation Cons: ○ Slices of time will be eaten. The smaller the slices the more overhead. Only large slices of 10s of milliseconds don't overly impact the overhead ○ Currently implemented userspace system doesn't account for interrupt execution time

Frequency Limiter Pros and Cons Pro: ● Simple, low overhead system. Cons: ● Requires a system that supports independent clock frequency changes. ● Most platforms only offer a few discrete operating points. To achieve a very precise level of performance degradation, you may need to add additional CPUFreq operating points.

CODE git://git.linaro.org/people/rob_lee/asymm_cpu_emu.git External Dependencies: ● schedtool ○ needed by cycle stealer to setting task priority

DEMO ● Cycle Stealer a. In one terminal, run cycle_stealer_mgr.sh as root b. In another terminal, run 'mpstat 2 -P ALL' to monitor amount of cpu idle time. ● Frequency Limiter a. In one terminal, run 'asymm_freq_limit.sh' b. In another terminal run ■ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq c. test ■ taskset 2 ./busy.sh ■ cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq ● veryify frequency is limited.

Add a comment

Related presentations

Presentación que realice en el Evento Nacional de Gobierno Abierto, realizado los ...

In this presentation we will describe our experience developing with a highly dyna...

Presentation to the LITA Forum 7th November 2014 Albuquerque, NM

Un recorrido por los cambios que nos generará el wearabletech en el futuro

Um paralelo entre as novidades & mercado em Wearable Computing e Tecnologias Assis...

Microsoft finally joins the smartwatch and fitness tracker game by introducing the...

Related pages

Cpus | LinkedIn

View 12913 Cpus posts, presentations, experts, and more. Get the professional knowledge you need on LinkedIn. LinkedIn Home What is LinkedIn? Join Today
Read more

MOS Technology 6502 - Wikipedia, the free encyclopedia

The 6502 is capable of performing addition ... could be run asymmetrically, increasing overall CPU ... 6502 compatible compiler and emulator written ...
Read more

Patent US20050216920 - Use of a virtual machine to emulate ...

A device virtual machine (VM) is configured to emulate a hardware device. The device VM includes device emulation code used to emulate the hardware device.
Read more

Patent US6991960 - Method of semiconductor device package ...

A method and apparatus for aligning a semiconductor device with a corresponding landing site on a carrier substrate. At least two apertures are formed in a ...
Read more

Energy Efficient Asymmetrically Ported Register Files

... we propose a novel asymmetrically ... The major bottleneck in performing crosstalk ... gate utilization of FPGAs and speed of emulation are ...
Read more

Brevetto US20050289317 - Method and related apparatus for ...

If data is stored in an asymmetrically arranged memory ... other devices or circuits with capable of performing direct ... Emulation of abstracted ...
Read more

Patent US5734119 - Method for streaming transmission of ...

An Internet high fidelity audio transmission and compression protocol including a system for representing synthesized music in a relatively small file as ...
Read more

Overview - Ni-Wumpf

... which is mounted asymmetrically ... performing file transfers, the CPU expects 1KByte Xmodem communications transfer protocol and the terminal emulator ...
Read more

Patent US8788690 - Systems and methods for providing ...

Systems and methods for managing and providing content and services on a network system. Aspects of the invention include location-based determination of ...
Read more