On Wed, Oct 24, 2012 at 7:59 AM, Yan, Zheng <zheng.z....@intel.com> wrote: > From: "Yan, Zheng" <zheng.z....@intel.com> > > Haswell has a new feature that utilizes the existing Last Branch Record > facility to record call chains. When the feature is enabled, function > call will be collected as normal, but as return instructions are executed > the last captured branch record is popped from the on-chip LBR registers. > The LBR call stack facility can help perf to get call chains of progam > without frame pointer. > > The LBR call stack has following known limitations > 1. Zero length calls are not filtered out by hardware > 2. Exception handing such as setjmp/longjmp will have calls/returns not > match > 3. Pushing different return address onto the stack will have calls/returns > not match > > The patch series depends on Andi's "perf PMU support for Haswel" patches > The part that is missing here is that you don't explain that you are now fitting LBR cstack under PERF_SAMPLE_CALLCHAIN. It is dynamically enabled based on users callstack request mode.
> --- > Changes since v1 > - not expose PERF_SAMPLE_BRANCH_CALL_STACK to user space > - save/restore LBR stack on context switch for all sampling branch modes > - reduce lbr_sel_map size -- 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/
