Dear all, I ran a full system simulation with four cores CPU, in which each core is hardcoded (using taskset command) to run a specific SPEC CPU2006 benchmarks (leslie3d, leslie3d, mcf, and mcf). The architecture of the simulated system can be inferred from the simulation command below:
build/X86/gem5.fast configs/example/fs.py --caches --disk-image=linux-x86-large.img --kernel=x86_64-vmlinux-3.2.24.smp --l1d_size=128kB --l1i_size=128kB --l2cache --l2_size=8MB --l2_assoc=8 --cacheline_size=64 -n 4 --mem-size=8GB --cpu-clock=4GHz --sys-clock=4GHz --mem-type=DDR3_1600_x64 --cpu-type=detailed -r 2 -I 250000000 Here is the result of the number of instructions and number of cycles simulated for each core: system.switch_cpus0.commit.committedInsts 276150 # Number of instructions committed system.switch_cpus1.commit.committedInsts 250000000 # Number of instructions committed system.switch_cpus2.commit.committedInsts 8546307 # Number of instructions committed system.switch_cpus3.commit.committedInsts 35930361 # Number of instructions committed system.switch_cpus0.numCycles 864447 # number of cpu cycles simulated system.switch_cpus1.numCycles 63273161 # number of cpu cycles simulated system.switch_cpus2.numCycles 6382626 # number of cpu cycles simulated system.switch_cpus3.numCycles 26166842 # number of cpu cycles simulated I can understand a small variation in the number of cycles/instructions between the cores; however, the variation in this case is huge. For example, why would the second core run faster than the first, even though they are running the same benchmark (leslie3d) with the same exact input (reference input)? In fact, the first core has an IPC of 0.32, while the second has an IPC of 3.95 (more that 10x faster). Also, is there a way to make the simulation fair, in the sense that each core is simulated for approximately the same number of cycles (or the same number of instructions)? Thank you, Ali.
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