Messages in this thread | | | From | kan.liang@linux ... | Subject | [PATCH 0/4] TopDown metrics support for Ice Lake (perf tool) | Date | Thu, 20 Aug 2020 09:45:28 -0700 |
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From: Kan Liang <kan.liang@linux.intel.com>
The kernel patches have been merged into the tip's perf/core branch. The patch set is on top of commit 2cb5383b30d4 ("perf/x86/intel: Support per-thread RDPMC TopDown metrics") of the tip's perf/core branch.
The changes for the perf tool include: - Extend --topdown option to support per thread TopDown metrics - Support sample-read topdown metric group - Add a complete document for the TopDown usage.
Ice Lake 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.
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
For the Ice Lake implementation of performance metrics, the values in PERF_METRICS MSR are derived from fixed counter 3. Software should start both registers, PERF_METRICS and fixed counter 3, from zero. Additionally, software is recommended to periodically clear both registers in order to maintain accurate measurements. The latter is required for certain scenarios that involve sampling metrics at high rates. Software should always write fixed counter 3 before write to PERF_METRICS.
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. Software has to synchronize, e.g. re-start, PERF_METRICS as well as fixed counter 3. Otherwise, PERF_METRICS may return invalid values.
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.
Andi Kleen (2): perf stat: Support new per thread TopDown metrics perf, tools: Add documentation for topdown metrics
Kan Liang (2): perf tools: Rename group to topdown perf record: Support sample-read topdown metric group
tools/perf/Documentation/perf-stat.txt | 7 +- tools/perf/Documentation/topdown.txt | 256 +++++++++++++++++++++++++ tools/perf/arch/x86/util/Build | 2 +- tools/perf/arch/x86/util/group.c | 28 --- tools/perf/arch/x86/util/topdown.c | 63 ++++++ tools/perf/builtin-stat.c | 81 +++----- tools/perf/util/Build | 1 + tools/perf/util/group.h | 8 - tools/perf/util/record.c | 3 +- tools/perf/util/stat-shadow.c | 89 +++++++++ tools/perf/util/stat.c | 4 + tools/perf/util/stat.h | 8 + tools/perf/util/topdown.c | 58 ++++++ tools/perf/util/topdown.h | 12 ++ 14 files changed, 528 insertions(+), 92 deletions(-) create mode 100644 tools/perf/Documentation/topdown.txt delete mode 100644 tools/perf/arch/x86/util/group.c create mode 100644 tools/perf/arch/x86/util/topdown.c delete mode 100644 tools/perf/util/group.h create mode 100644 tools/perf/util/topdown.c create mode 100644 tools/perf/util/topdown.h
-- 2.17.1
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