[PATCH 4/4] perf docs: Update SPE doc to include default instructions group

James Clark
2025-09-08T17:08:26Z

The instructions group is now generated by default so update the doc to
reflect this. Also explain the period/downsampling mechanism in more
detail.

Signed-off-by: James Clark <james.clark@linaro.org>
---
tools/perf/Documentation/perf-arm-spe.txt | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/Documentation/perf-arm-spe.txt b/tools/perf/Documentation/perf-arm-spe.txt
index 37afade4f1b2..cda8dd47fc4d 100644
--- a/tools/perf/Documentation/perf-arm-spe.txt
+++ b/tools/perf/Documentation/perf-arm-spe.txt
@@ -191,14 +191,20 @@ groups:
36 branch
0 remote-access
900 memory
+ 1800 instructions

The arm_spe// and dummy:u events are implementation details and are expected to be empty.

-To get a full list of unique samples that are not sorted into groups, set the itrace option to
-generate 'instruction' samples. The period option is also taken into account, so set it to 1
-instruction unless you want to further downsample the already sampled SPE data:
+The instructions group contains the full list of unique samples that are not
+sorted into other groups. To generate only this group use --itrace=i1i.

- perf report --itrace=i1i
+1i (1 instruction interval) signifies no further downsampling. Rather than an
+instruction interval, this generates a sample every n SPE samples. For example
+to generate the default set of events for every 100 SPE samples:
+
+ perf report --itrace==bxofmtMai100i
+
+Other period types, for example nanoseconds (ns) are not currently supported.

Memory access details are also stored on the samples and this can be viewed with:

--
2.34.1