> - Independently, when I add a custom printk manually in `arch/x86/events/ > intel/ds.c` at the end of `setup_pebs_sample_data`, then I'm never seeing any > differences between SP in iregs/pebs/regs. Shouldn't it also be recorded via > PEBS? Or is it just chance that I'm never seeing any difference in > setup_pebs_sample_data between iregs->sp and regs->sp?
It will depend on the workload. > > - Generally, how do we want to handle this bug? If `--intr-regs` would > actually record a different IP than stored in uregs in the perf.data file, > then we could use that as a fallback for unwinding, when it fails the first > time. Or should we always unwind from that IP? How do we mark the "actual" > frame/IP then, if that differs? I don't think the regs include IP currently? Would need to add it. Then could report everything from the original stack in intr-regs, and this would address that problem. Yes it might be useful to add some indication to the sample that there is a potential divergence between the backtrace and the IP. Would also need to report that in perf report then. -Andi
