ChampSim

Compile

ChampSim takes five parameters: Branch predictor, L1D prefetcher, L2C prefetcher, LLC replacement policy, and number of cores. For example, ./build_champsim.sh bimodal no no lru 1 builds a single-core processor with bimodal branch predictor, no L1/L2 data prefetchers, and the baseline LRU replacement policy for the LLC.

$ ./build_champsim.sh bimodal no no lru 1

$ ./build_champsim.sh ${BRANCH} ${L1D_PREFETCHER} ${L2C_PREFETCHER} ${LLC_REPLACEMENT} ${NUM_CORE}

Run simulation

Copy scripts/run_champsim.sh to the ChampSim root directory

• Single-core simulation: Run simulation with run_champsim.sh script.

$ ./run_champsim.sh bimodal-no-no-lru-1core 1 10 bzip2

$ ./run_champsim.sh ${binary} ${n_warm} ${n_sim} ${trace} ${option}

${binary}: ChampSim binary compiled by "build_champsim.sh" (bimodal-no-no-lru-1core)
${n_warm}: number of instructions for warmup (1 million)
${n_sim}:  number of instructinos for detailed simulation (10 million)
${trace}: trace name (bzip2)
${option}: extra option for "-low_bandwidth" (src/main.cc)

Simulation results will be stored under "results_${n_sim}M" as a form of "${trace}-${binary}-${option}.txt".

• Multi-core simulation: Run simulation with run_4core.sh or run_8core.sh.
  Note that ${trace} is replaced with ${num} that represents a unique mixed workload ID for multi-programmed workloads.

$ ./run_4core.sh ${binary} ${n_warm} ${n_sim} ${num} ${option}

${num}: mix number is the corresponding line number written in sim_list/4core_workloads.txt

Add your own branch predictor, data prefetchers, and replacement policy

Copy an empty template

$ cp branch/branch_predictor.cc prefetcher/mybranch.bpred
$ cp prefetcher/l1d_prefetcher.cc prefetcher/mypref.l1d_pref
$ cp prefetcher/l2c_prefetcher.cc prefetcher/mypref.l2c_pref
$ cp replacement/llc_replacement.cc replacement/myrepl.llc_repl

Work on your algorithms with your favorite text editor

$ vim branch/mybranch.bpred
$ vim prefetcher/mypref.l1d_pref
$ vim prefetcher/mypref.l2c_pref
$ vim replacement/myrepl.llc_repl

Compile and test

$ ./build_champsim.sh mybranch mypref mypref myrepl 1
$ ./run_champsim.sh mybranch-mypref-mypref-myrepl-1core 1 10 bzip2

How to create traces

We have included some sample traces, taken from SPEC CPU 2006 with SimPoint methodology. The included Pin Tool champsim_tracer.so can be used to generate new traces. It was created using Pin 3.0 (pin-3.0-76991-gcc-linux), and may require installing libdwarf.so, libelf.so, or other libraries, if you do not already have them. Please refer to Pin documentation for working with Pin 3.0.

Use the Pin tool like this

pin -t lib/champsim_tracer.so -- <your program here>

The tracer has three options you can set:

-o
Specify the output file for your trace.
The default is default_trace.champsim

-s <number>
Specify the number of instructions to skip in the program before tracing begins.
The default value is 0.

-t <number>
The number of instructions to trace, after -s instructions have been skipped.
The default value is 1,000,000.

For example, you could trace 200,000 instructions of the program ls, after skipping the first 100,000 instructions, with this command:

pin -t lib/champsim_tracer.so -o traces/ls_trace.champsim -s 100000 -t 200000 -- ls

Traces created with the champsim_tracer.so are 60 bytes per instruction, but they generally compress down to 2-10 bytes per instruction using gzip.

Evaluate Simulation

ChampSim measures the IPC (Instruction Per Cycle) value as a performance metric.
There are also some useful shell scripts located under scripts/ directory.