[PATCH V4 00/14] TopDown metrics support for Icelake

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

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

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2.17.1