On 11/08/13 22:46, Matt Sealey wrote: > On Fri, Nov 8, 2013 at 5:00 PM, Stephen Boyd <sb...@codeaurora.org> wrote: >> If we're running on a v7 ARM CPU, detect if the CPU supports the >> sdiv/udiv instructions and replace the signed and unsigned >> division library functions with an sdiv/udiv instruction. >> >> Running the perf messaging benchmark in pipe mode >> >> $ perf bench sched messaging -p >> >> shows a modest improvement on my v7 CPU. >> >> before: >> (5.060 + 5.960 + 5.971 + 5.643 + 6.029 + 5.665 + 6.050 + 5.870 + 6.117 + >> 5.683) / 10 = 5.805 >> >> after: >> (4.884 + 5.549 + 5.749 + 6.001 + 5.460 + 5.103 + 5.956 + 6.112 + 5.468 + >> 5.093) / 10 = 5.538 >> >> (5.805 - 5.538) / 5.805 = 4.6% > Even with the change to the output constraint suggested by Mans, you > get absolutely identical benchmark results? There's a lot of variance > in any case..
Yeah sorry I didn't run the testcase again to see if numbers changed because I assumed one less instruction would be in the noise. I agree there is a lot of variance so if you have any better benchmarks/testcases please let me know. > > BTW has there been any evaluation of the penalty for the extra > branching, or the performance hit for the ARMv7-without-division > cases? I haven't done any. I'll factor that in for the next round. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
