perf Document: Add TPEBS (Timed PEBS(Precise Event-Based Sampling)) to Documents

TPEBS (Timed PEBS(Precise Event-Based Sampling)) is a new feature Intel
PMU from Granite Rapids microarchitecture.

It will be used in new TMA (Top-Down Microarchitecture Analysis)
releases.

Add related introduction to documents while adding new code to support
it in 'perf stat'.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Weilin Wang <weilin.wang@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Samantha Alt <samantha.alt@intel.com>
Link: https://lore.kernel.org/r/20240720062102.444578-8-weilin.wang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt
index 6bf2468f59d31df7d85913afb00f8f5bf6b1472f..dea005410ec02fed9d46599ce7c07a7467dd9ced 100644 (file)
--- a/tools/perf/Documentation/perf-list.txt
+++ b/tools/perf/Documentation/perf-list.txt
@@ -72,6 +72,7 @@ counted. The following modifiers exist:
  W - group is weak and will fallback to non-group if not schedulable,
  e - group or event are exclusive and do not share the PMU
  b - use BPF aggregration (see perf stat --bpf-counters)
+ R - retire latency value of the event
 
 The 'p' modifier can be used for specifying how precise the instruction
 address should be. The 'p' modifier can be specified multiple times:

diff --git a/tools/perf/Documentation/topdown.txt b/tools/perf/Documentation/topdown.txt
index ae0aee86844fe394cd919769a3b7933de90a69b4..5c17fff694ee7d6dc0d184a550d7fa30a3166b5f 100644 (file)
--- a/tools/perf/Documentation/topdown.txt
+++ b/tools/perf/Documentation/topdown.txt
@@ -325,6 +325,36 @@ other four level 2 metrics by subtracting corresponding metrics as below.
     Fetch_Bandwidth = Frontend_Bound - Fetch_Latency
     Core_Bound = Backend_Bound - Memory_Bound
 
+TPEBS in TopDown
+================
+
+TPEBS (Timed PEBS) is one of the new Intel PMU features provided since Granite
+Rapids microarchitecture. The TPEBS feature adds a 16 bit retire_latency field
+in the Basic Info group of the PEBS record. It records the Core cycles since the
+retirement of the previous instruction to the retirement of current instruction.
+Please refer to Section 8.4.1 of "Intel® Architecture Instruction Set Extensions
+Programming Reference" for more details about this feature. Because this feature
+extends PEBS record, sampling with weight option is required to get the
+retire_latency value.
+
+       perf record -e event_name -W ...
+
+In the most recent release of TMA, the metrics begin to use event retire_latency
+values in some of the metrics’ formulas on processors that support TPEBS feature.
+For previous generations that do not support TPEBS, the values are static and
+predefined per processor family by the hardware architects. Due to the diversity
+of workloads in execution environments, retire_latency values measured at real
+time are more accurate. Therefore, new TMA metrics that use TPEBS will provide
+more accurate performance analysis results.
+
+To support TPEBS in TMA metrics, a new modifier :R on event is added. Perf would
+capture retire_latency value of required events(event with :R in metric formula)
+with perf record. The retire_latency value would be used in metric calculation.
+Currently, this feature is supported through perf stat
+
+       perf stat -M metric_name --record-tpebs ...
+
+
 
 [1] https://software.intel.com/en-us/top-down-microarchitecture-analysis-method-win
 [2] https://sites.google.com/site/analysismethods/yasin-pubs