On Mon, Mar 2, 2015 at 4:19 PM, Vince Weaver <vincent.weaver@xxxxxxxxx> wrote: > On Mon, 2 Mar 2015, Stephane Eranian wrote: > >> vince, > >> PEBS machine state. Problem is that there is only one set of pt_regs passed to >> __intel_pmu_pebs_event(). And if REGS_INTR is set, then the pt_regs >> registers are >> indeed overwritten with PEBS captured state. To avoid the issue, we >> would have to >> carry around two sets of pt_regs. > > I don't think we have to carry around both (would that ever be useful?) > Just that the behavior is a bit surprising and I should document it in the > manpage. > > One question I do have: if it never makes sense to measure REGS_USER and > REGS_INTR at the same time, why was the latter added at all? Why not just > have the REGS_USER information automatically upgrade to REGS_INTR if > precise_ip is high enough? > Vince, REGS_USER is user ONLY. It does not capture machine state if PMU interrupt occurred inside the kernel. REGS_USER is useful in support of dwarf based user level call stack unwinding. Otherwise REGS_INTR is what most analysis tools need. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
