Messages in this thread | | | From | James Clark <> | Subject | [PATCH v1 0/2] arm64: perf: Add support for event counting threshold | Date | Tue, 19 Sep 2023 10:51:27 +0100 |
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FEAT_PMUv3_TH (Armv8.8) is a new feature that allows conditional counting of PMU events depending on how much the event increments on a single cycle. Two new config fields for perf_event_open have been added, and a PMU cap file for reading the max_threshold. See the first commit message and the docs in the second commit for more details.
The change has been validated on the Arm FVP model:
# Zero values, works as expected (as before). $ perf stat -e dtlb_walk/threshold=0,threshold_control=0/ -- true
5962 dtlb_walk/threshold=0,threshold_control=0/
# Threshold >= 255 causes count to be 0 because dtlb_walk doesn't # increase by more than 1 per cycle. $ perf stat -e dtlb_walk/threshold=255,threshold_control=5/ -- true
0 dtlb_walk/threshold=255,threshold_control=5/
# Keeping comparison as >= but lowering the threshold to 1 makes the # count return. $ perf stat -e dtlb_walk/threshold=1,threshold_control=5/ -- true
6329 dtlb_walk/threshold=1,threshold_control=5/
James Clark (2): arm64: perf: Add support for event counting threshold Documentation: arm64: Document the PMU event counting threshold feature
Documentation/arch/arm64/perf.rst | 58 ++++++++++++++++++++++++++++++ drivers/perf/arm_pmuv3.c | 59 ++++++++++++++++++++++++++++++- include/linux/perf/arm_pmuv3.h | 7 +++- 3 files changed, 122 insertions(+), 2 deletions(-)
base-commit: 21b61fe48c2fc43d98ebb67a1f3832e0478fa523 -- 2.34.1
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