Table of contents

1. File Path Setting
2. Enviornment
3. Declaring Simobject
4. Add option for Ramulator config file

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File Path Setting

gem5/
├── configs/ 
│   |
│   └── common/
│       |- MemConfig.py
│       |- Options.py
│       └─ ...
|   
├── src/ 
│   └── mem/
│ 	|- ramulator2.cc ramualator.hh
│ 	|- Ramulator2.py
│ 	|- SConscript
│ 	└─ ...
│
├── ext/  # not guided in this docs
│  └── ramulator2/
│ 	|- SConscript
│ 	└─ ramulator2/  
│ 	    |- src/
│ 	    |- libramulator.so
│ 	    └─ ...

• Above tree shows overall files which requires modification to integrate gem5 and ramulator2 and its path

You can get all complete code at my github.. This docs mainly guides how to integrate ramulator with gem5 and its required modification. To run ramulator2 locally, please refer to ramulator2 official repo

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Enviornment

• >= Ubuntu22.04 (due to support on c++23)
• c++-12 (apt-get install c++-12)
• clang++-15 (apt-get install clang clang++-15)
• cmake
• gem5 ver.22.0

---

Declaring Simobject

# gem5/src/mem/SConscript
if env['HAVE_RAMULATOR2']:
    SimObject("Ramulator2.py", sim_objects=['Ramulator2'])
    Source("ramulator2.cc")
    DebugFlag("Ramulator2")

• SimObject(“Ramulator2.py”…): Add class “Ramulator2” as a simobject.
• Source(“ramulator2.cc”): compile the predefined c++ wrapper code.
• DebugFlag(“Ramulator2”): (optional), add “Ramulator2” as one of gem5 debug flag

# gem5/src/mem/Ramulator2.py
from m5.SimObject import *
from m5.params import *
from m5.objects.AbstractMemory import *

class Ramulator2(AbstractMemory):
    type = "Ramulator2"
    cxx_class = "gem5::memory::Ramulator2"
    cxx_header = "mem/ramulator2.hh"
    port = ResponsePort("The port for receiving memory requests and sending responses")

• Defines the python class for Ramulator2
• While compiling, gem5 follows cxx_headers path and reach cxx_class instance

---

# gem5/common/MemConfig.py config_mem() new code
...
if issubclass(intf, m5.objects.Ramulator2):
    mem_ctrl = dram_intf
else:
    mem_ctrl = dram_intf.controller()
...

• While the conventional dram class returns dram interface instance by calling function called controller(), Ramulator2 is not
• Connect it to dram_intf

---

Add option for Ramulator config file

# gem5/configs/common/Options.py
...
parser.add_argument(
    "--ramulator-config",
    type=str,
    dest="ramulator_config",
    help="inputs ramulator configuration file"
)
...

• Now, the option --ramulator-config is added

# gem5/configs/common/MemConfig.py create_mem_intf()
...
if issubclass(intf, m5.objects.Ramualator2):
    if not options.ramulator_config:
        print("--mem-type=Ramulator2 requires options --ramulator-config")
        exit(1)
    interface.config_path = options.ramulator_config
...

• Connect the option to Ramulator2 simobject
• interface is an instance of python-defined Ramulator2 class
• options.ramualtor_config comes from previous subsection

# gem5/src/mem/Ramulator2.py
from m5.SimObject import *
from m5.params import *
from m5.objects.AbstractMemory import *

class Ramulator2(AbstractMemory):
    type = "Ramulator2"
    cxx_class = "gem5::memory::Ramulator2"
    cxx_header = "mem/ramulator2.hh"
    port = ResponsePort("The port for receiving memory requests and sending responses")

    #NOTE newly added to accommodate config file
    config_path = Param.String("", "--ramulator-config")

• Define new varialbe in python class to accommodate the new option
• Compiling gem5, param/Ramulator2.hh adds new string variable config_path

# gem5/src/mem/ramualtor2.hh
namespace gem5 {
namespace memory {
class Ramulator2 : public AbstractMemory {
...
private:
    std::string config_path;
...
}
}}

# gem5/src/mem/ramualtor2.cc
Ramulator2::Ramulator2(const Params &p){ // Constructor
config_path = p.config_path;
YAML::Node config = parse_config(config_path); // this is pseudo-code
}

• In wrapper code, you can call the config_path by referencing member variable of Params which comes from param/Ramulator2.hh

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