[PATCH v1 0/8] Add core wide metric literal

Ian Rogers
2022-08-30T16:49:01Z

It is possible to optimize metrics when all SMT threads (CPUs) on a
core are measuring events in system wide mode. For example, TMA
metrics [1] defines CORE_CLKS for Sandybrdige as:

if SMT is disabled:
CPU_CLK_UNHALTED.THREAD
if SMT is enabled and recording on all SMT threads (for all processes):
CPU_CLK_UNHALTED.THREAD_ANY / 2
if SMT is enabled and not recording on all SMT threads:
(CPU_CLK_UNHALTED.THREAD/2)*
(1+CPU_CLK_UNHALTED.ONE_THREAD_ACTIVE/CPU_CLK_UNHALTED.REF_XCLK )

That is two more events are necessary when not gathering counts on all
SMT threads. To distinguish all SMT threads on a core vs system wide
(all CPUs) call the new property core wide.

As this literal requires the user requested CPUs and system wide to be
present, the parsing of metrics is delayed until after command line
option processing. As events are used to compute the evlist maps, and
metrics create events, the data for core wide must come from the target.

This patch series doesn't correct the Intel metrics to use #core_wide,
which will be done in follow up work. To see the two behaviors
currently you need an Intel CPU between Sandybridge and before
Icelake, then compare the events for tma_backend_bound_percent and
Backend_Bound_SMT where the former assumes recording on all SMT
threads and the latter assumes not recording on all SMT threads. The
future work will just have a single backend bound metric for both
cases determined using #core_wide.

[1] https://download.01.org/perfmon/TMA_Metrics.xlsx Note, #EBS_Mode
is false when recording on all SMT threads and all processes which is
#core_wide true in this change.

Ian Rogers (8):
perf smt: Tidy header guard add SPDX
perf metric: Return early if no CPU PMU table exists
perf expr: Move the scanner_ctx into the parse_ctx
perf smt: Compute SMT from topology
perf topology: Add core_wide
perf stat: Delay metric parsing
perf metrics: Wire up core_wide
perf test: Add basic core_wide expression test

tools/perf/builtin-stat.c | 57 +++++++++++++-----
tools/perf/tests/expr.c | 37 +++++++++---
tools/perf/util/cputopo.c | 61 +++++++++++++++++++
tools/perf/util/cputopo.h | 5 ++
tools/perf/util/expr.c | 26 ++++----
tools/perf/util/expr.h | 14 +++--
tools/perf/util/expr.l | 6 +-
tools/perf/util/metricgroup.c | 92 +++++++++++++++++++++-------
tools/perf/util/metricgroup.h | 4 +-
tools/perf/util/smt.c | 110 ++++++++--------------------------
tools/perf/util/smt.h | 19 ++++--
tools/perf/util/stat-shadow.c | 13 ++--
tools/perf/util/stat.h | 2 +
13 files changed, 286 insertions(+), 160 deletions(-)

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2.37.2.672.g94769d06f0-goog