[PATCH 2/2] perf cs-etm: Centralize branch sample checks
From: Leo Yan <leo.yan@arm.com>
Date: 2026-07-13 18:00:54
Also in:
linux-perf-users, lkml
Subsystem:
arm/coresight framework and drivers, performance events subsystem, performance events tooling arm64, the rest · Maintainers:
Suzuki K Poulose, Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds
cs_etm__sample() validates whether the previous packet should generate
a branch sample before calling cs_etm__synth_branch_sample(), while
cs_etm__flush() generates branch samples unconditionally.
Move the eligibility check into cs_etm__synth_branch_sample() so that
both paths apply the same rule: generate branch samples only for
discontinuity packets or range packets ending in a taken branch.
Fixes: d603b4e9f9c3 ("perf cs-etm: Generate branch sample when receiving a CS_ETM_TRACE_ON packet")
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
tools/perf/util/cs-etm.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 05e698f666bbe07af9caeda1a673f22d7196817a..dec50e2cc7b7857a04f631b3e0e08beb6e7e280a 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c@@ -1710,6 +1710,11 @@ static int cs_etm__synth_branch_sample(struct cs_etm_queue *etmq, !(etm->branches_filter & tidq->prev_packet->flags)) return 0; + /* Generate branch sample only for tracing on or taken branches */ + if (tidq->prev_packet->sample_type != CS_ETM_DISCONTINUITY && + !cs_etm__packet_has_taken_branch(tidq->prev_packet)) + return 0; + perf_sample__init(&sample, /*all=*/true); ip = cs_etm__last_executed_instr(tidq->prev_packet);
@@ -1946,21 +1951,9 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, } if (etm->synth_opts.branches) { - bool generate_sample = false; - - /* Generate sample for tracing on packet */ - if (tidq->prev_packet->sample_type == CS_ETM_DISCONTINUITY) - generate_sample = true; - - /* Generate sample for branch taken packet */ - if (cs_etm__packet_has_taken_branch(tidq->prev_packet)) - generate_sample = true; - - if (generate_sample) { - ret = cs_etm__synth_branch_sample(etmq, tidq); - if (ret) - return ret; - } + ret = cs_etm__synth_branch_sample(etmq, tidq); + if (ret) + return ret; } cs_etm__packet_swap(etm, tidq);
--
2.34.1