This project is based on the gem5-NVP. (Latest update: 2017/06/30)

The gem5-NVP is a simulating framework for non-volatile processors (NVP) and non-volatile systems based on the gem5 simulator. It provides multiple interfaces for adding description of SimObjects' energy behavior as well as an energy management module which allows users to simulate state changes (power-on, power-off, etc.) easily.

Below is the overview of our designed system for two-threshold/frequency NVP. Basically we maintain 3 classes here, Energy Management, ClockDomain and AtomicSimpleCPU. During the communication among these units, ports of Energy Management serves as the master, whereas ports of AtomicSimpleCPU and ClockDomain serve as slave.

Energy Management module is able to broadcast message to slave ports, and slave ports will handle messages sent and take responding actions. Each tick cycle, Energy Management module will first compute the net value of energy harvested and consumed. After that, it will examine its energy threshold, that is to say, if the current energy is above the higher threshold, message standing for high frequency will be broadcast, and if the current energy is below the lower threshold, message for powering off will be broadcast.

AtomicSimpleCPU will reflect on the message by schedule or deschedule into eventqueue. A power-off message means that this processor needs to be shut down, so deschedule() will be called.

ClockDomain will adjust its CPU clock frequency, i.e. the performance level of CPU, based on message it received

See Report.

Gem5-NVP depends on nothing besides the dependencies of gem5 simulator. Tools needed before building gem5-NVP can be found at http://www.gem5.org/Dependencies.

The build process of gem5-NVP is almost the same as gem5 simulator. Scons is used to build target system to be simulated. Theoretically, different ISAs are supported by gem5-NVP. However, gem5-NVP is tested under ARM, so the following build option is recommended:

mv README.md README
scons build/ARM/gem5.debug

One tricky thing is that gem5 checks its original raw README during its build, so we can simply rename README.md into README. Markdown file is used only for better github page.

Gem5-nvp provides an alternated script based on "./configs/example/se.py" to simulate energy-related systems, using System Call Emulation Mode in gem5. The path to the script is "./configs/example/se_engy.py". Gem5-nvp has several interfaces for users to control the energy behavior of the whole system. Most of the interfaces present as arguments of the "se_engy.py" script, while others (mostly debug output control) present as arguments of the target system such as "build/ARM/gem5.debug". Note: Target system in gem5 already receives arguments to control debug output, and gem5-NVP only adds some debug flags for energy behavior.

The following examples will simulate systems running "./test/test-progs/hello/bin/arm/linux/hello". To run exactly like gem5 (No energy behavior is simulated):

build/ARM/gem5.debug configs/example/se_engy.py -c tests/test-progs/hello/bin/arm/linux/hello

To simulate atomic cpu's energy behavior, using energy profile "./profile/energy_prof", with energy_time_unit = 100, printing all the debug information of energy behavior into "./m5out/a.out":

build/ARM/gem5.debug --debug-flags=EnergyMgmt --debug-file=a.out configs/example/se_engy.py -c tests/test-progs/hello/bin/arm/linux/hello --energy-profile=./profile/energy_prof --energy-time-unit=100 --energy-modules='cpu'

Gem5-NVP also supports more advanced functions which require developers to modify source code, like simulating systems with 2-threshold energy state machine. Tutorials and examples of such usage can be found at https://github.com/zlfben/gem5/wiki.

This is the gem5 simulator.

The main website can be found at http://www.gem5.org

A good starting point is http://www.gem5.org/Introduction, and for more information about building the simulator and getting started please see http://www.gem5.org/Documentation and http://www.gem5.org/Tutorials.

To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/Dependencies for more details concerning the minimum versions of the aforementioned tools.

Once you have all dependencies resolved, type 'scons build//gem5.opt' where ARCH is one of ALPHA, ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/Build_System for more details and options.

With the simulator built, have a look at http://www.gem5.org/Running_gem5 for more information on how to use gem5.

The basic source release includes these subdirectories:

• configs: example simulation configuration scripts
• ext: less-common external packages needed to build gem5
• src: source code of the gem5 simulator
• system: source for some optional system software for simulated systems
• tests: regression tests
• util: useful utility programs and files

To run full-system simulations, you will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. Please see the gem5 download page for these items at http://www.gem5.org/Download

If you have questions, please send mail to gem5-users@gem5.org

Enjoy using gem5 and please share your modifications and extensions.