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. 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 main change since previous patch series is: Patch 3 introduces PMU context switch callback, and uses the callback to unify the flush branch stack codeo. Patch 4 uses the context switch callback to save/restore the LBR stack. Regards Yan, Zheng -- 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/
