> > On Fri, 14 Nov 2014 08:44:10 -0500, kan liang wrote: > > From: Kan Liang <kan.li...@intel.com> > > > > Currently, there are two call chain recording options, fp and dwarf. > > Haswell has a new feature that utilizes the existing LBR facility to > > record call chains. So it provides the third options to record call > > chain. This patch enables the lbr call stack support. > > > > LBR call stack has some limitations. It reuses current LBR facility, > > so LBR call stack and branch record can not be enabled at the same > > time. It is only available for user callchain. > > However, LBR call stack can work on the user app which doesn't have > > frame-pointer or dwarf debug info compiled. It is a good alternative > > when nothing else works. > > So this is only for Haswell or later, right?
Right. >What if user gives it to the other > CPUs - is it fail or ignore silently? I think we need to warn user about it > more kindly.. The kernel will handle it. EOPNOTSUPP will be return if there is no LBR Call stack support. Thanks, Kan > > Thanks, > Namhyung -- 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/