From: Kan Liang <kan.li...@linux.intel.com> Icelake has support for measuring the level 1 TopDown metrics directly in hardware. This is implemented by an additional METRICS register, and a new Fixed Counter 3 that measures pipeline SLOTS.
For the Ice Lake implementation of performance metrics, software should start both PERF_METRICS and fixed counter 3 from zero. Additionally, for certain scenarios that involve counting metrics at high rates, software is recommended to periodically clear both in order to maintain accurate measurements. IA32_PERF_GLOBAL_STATUS. OVF_PERF_METRICS[48]: If this bit is set, it indicates that some PERF_METRICS-related counter has overflowed and a PMI is triggered. It is recommended to clear PERF_METRICS as well as fixed counter 3 in such case. However, an overflow of fixed counter 3 should normally happen first. If this bit is clear, no such overflow has occurred. New in Icelake - Do not require generic counters. This allows to collect TopDown always in addition to other events. - Measuring TopDown per thread/process instead of only per core Limitation - To get accurate result and avoid reading the METRICS register multiple times, the TopDown metrics events and SLOTS event have to be in the same group. - METRICS and SLOTS registers have to be cleared after each read by SW. That is to prevent the lose of precision. - Cannot do sampling read SLOTS and TopDown metric events Please refer SDM Vol3, 18.3.9.3 Performance Metrics for the details of TopDown metrics. Changes since V3: - Separate fixed counter3 definition patch - Separate BTS index patch - Apply Peter's cleanup patch - Fix the name of perf capabilities for perf METRICS - Apply patch for mul_u64_u32_div() x86_64 implementation - Fix unconditionally allows collecting 4 extra events - Add patch to clean up NMI handler by naming global status bit - Add patch to reuse event_base_rdpmc for RDPMC userspace support Changes since V2: - Rebase on top of v5.3-rc1 Key changes since V1: - Remove variables for reg_idx and enabled_events[] array. The reg_idx can be calculated by idx in runtime. Using existing active_mask to replace enabled_events. - Choose value 47 for the fixed index of BTS. - Support OVF_PERF_METRICS overflow bit in PMI handler - Drops the caching mechanism and related variables New mechanism is to update all active slots/metrics events for the first slots/metrics events in a group. For each group reading, it still only read the slots/perf_metrics MSR once - Disable PMU for read of topdown events to avoid the NMI issue - Move RDPMC support to a separate patch - Using event=0x00,umask=0x1X for topdown metrics events - Drop the patch which add REMOVE transaction We can indicate x86_pmu_stop() by checking (event && !test_bit(event->hw.idx, cpuc->active_mask)), which is a good place to save the slots/metrics MSR value Andi Kleen (2): perf, tools, stat: Support new per thread TopDown metrics perf, tools: Add documentation for topdown metrics Kan Liang (11): perf/x86/intel: Introduce the fourth fixed counter perf/x86/intel: Set correct mask for TOPDOWN.SLOTS perf/x86/intel: Move BTS index to 47 perf/x86/intel: Basic support for metrics counters perf/x86/intel: Fix the name of perf capabilities for perf METRICS perf/x86/intel: Support hardware TopDown metrics perf/x86/intel: Support per thread RDPMC TopDown metrics perf/x86/intel: Export TopDown events for Icelake perf/x86/intel: Disable sampling read slots and topdown perf/x86/intel: Name global status bit in NMI handler perf/x86: Use event_base_rdpmc for RDPMC userspace support Peter Zijlstra (Intel) (1): x86/math64: Provide a sane mul_u64_u32_div() implementation for x86_64 arch/x86/events/core.c | 80 ++++- arch/x86/events/intel/core.c | 421 +++++++++++++++++++++++-- arch/x86/events/perf_event.h | 57 +++- arch/x86/include/asm/div64.h | 13 + arch/x86/include/asm/msr-index.h | 3 + arch/x86/include/asm/perf_event.h | 48 ++- include/linux/perf_event.h | 3 + tools/perf/Documentation/perf-stat.txt | 9 +- tools/perf/Documentation/topdown.txt | 223 +++++++++++++ tools/perf/builtin-stat.c | 24 ++ tools/perf/util/stat-shadow.c | 89 ++++++ tools/perf/util/stat.c | 4 + tools/perf/util/stat.h | 8 + 13 files changed, 924 insertions(+), 58 deletions(-) create mode 100644 tools/perf/Documentation/topdown.txt -- 2.17.1
