2 ms·

I don't know how rdcycle works on qemu. This benchmark is more meant for developers to figure out how to vectorize algorithms effectively, as in which instructi

• rwmj 3y ago
  > I don't know how rdcycle works on qemu. That's a good question! I had to look it up myself ... Obviously qemu TCG isn't a cycle-accurate emulation. Using RDCYCLE{,H} / reading the corresponding CSRs eventually calls https://gitlab.com/qemu-project/qemu/-/blob/69680740eafa1838527c90155a7432d51b8ff203/target/riscv/csr.c#L759 https://gitlab.com/qemu-project/qemu/-/blob/69680740eafa1838... which calls cpu_get_host_ticks which is basically an arch-independent wrapper around RDTSC, assuming you are running qemu on x86 host. I think icount_enabled is false in normal qemu builds. Therefore it would measure the time taken by qemu to emulate the vector instruction, in host instructions. Which I guess is what you would want (maybe?). > This benchmark is more meant for developers to figure out how to vectorize algorithms effectively, as in which instructions to choose. Absolutely, I'm not saying the qemu results would say anything very deep, but they're kind of interesting from the point of view of either optimizing qemu or if you have to use qemu because the hardware you want isn't available / isn't cheap enough.