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Say if I am running an ARM simulator using Qemu, is it possible to find the time of execution of a program as it would be on the real ARM processor. In other words if I use functions such as gettimeofday, in a program running on the simulator, to check the elapsed time, will the elapsed time be given accurately through the cycle-accurate simulation?
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Investigation in this issue at our company concluded that Qemu (for the ARM) is not cycle accurate. If I remember correctly cycle accuracy is not a goal of Qemu, instead it aims at fast emulation. Beware also that exact timing is dependent on quite unpredictable things like cache hits and misses.
QEMU can boot many guest operating systems, including Linux, Solaris, Microsoft Windows, DOS, and BSD; it supports emulating several instruction sets, including x86, MIPS, 32-bit ARMv7, ARMv8, PowerPC, SPARC, ETRAX CRIS and MicroBlaze.
QEMU can emulate both 32-bit and 64-bit Arm CPUs. Use the qemu-system-aarch64 executable to simulate a 64-bit Arm machine.
Investigation in this issue at our company concluded that Qemu (for the ARM) is not cycle accurate. If I remember correctly cycle accuracy is not a goal of Qemu, instead it aims at fast emulation. Beware also that exact timing is dependent on quite unpredictable things like cache hits and misses. It will also depend on the actual architecture chosen. Note that ARM is merely an instruction set IP and several different implementations exist. If in addition an operating system is emulated, things get even more unpredictable.
We use the simulator from ARM to evaluate performance, but even that one is not fully cycle accurate for the latest versions of the ARM architecture.
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