Hi, While playing with perf tool on ARMv7 and ARCv2 processors and profiling the same application I got interesting results. Even if we got pretty similar total execution time and instructions number the number of branches on ARC is about three times more then on ARM. I dug into architecture specific perf sources and found that we map different HW counters into generic 'branches' event on ARC and ARM. - We use "ijmp" event on ARC which counts all jump and branch instructions (regardless of real execution flow - even if no real jump happens) - We use "pc_write_retired" event on ARM which counts only taken branches (Instruction architecturally executed, condition check pass - software change of the PC) So I was wondering do you know which approach is correct? I guess counting all jump and branch instructions is correct because we use 'branches' event value to calculate relative value of 'branch-misses' using following formula: ----------------------------8---------------------------- branch-misses-ration = 'branch-misses' / 'branches' * 100.0 ---------------- ------------8---------------------------- And using only taken branches here is incorrect IMHO. So I guess we should map 'br_immed_retired' instead of "pc_write_retired" into generic 'branches' event on ARM. -- Eugeniy Paltsev _______________________________________________ linux-snps-arc mailing list linux-snps-arc@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-snps-arc
