On Tue, Jun 25, 2013 at 10:47 AM, Yan, Zheng <[email protected]> wrote: > From: "Yan, Zheng" <[email protected]> > > 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. When perf tool requests PERF_SAMPLE_CALLCHAIN + > PERF_SAMPLE_BRANCH_USER, this feature is dynamically enabled by default. > This feature can be disabled/enabled through an attribute file in the cpu > pmu sysfs directory. > > 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 > I would also add that it does not work with leaf call optimizations: A calls B, B calls C, C returns to A
and that can be fairly common with small functions. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
