Re: [PATCH v1 2/3] perf arm-spe: Correct sample flags for dummy event
From: James Clark <hidden>
Date: 2021-05-12 14:40:03
Also in:
linux-arm-kernel, lkml
On 29/04/2021 18:00, Leo Yan wrote:
quoted hunk ↗ jump to hunk
The dummy event is mainly used for mmap, the TIME sample is only needed for per-cpu case so that the perf tool can rely on the correct timing for parsing symbols. And the CPU sample is useless for mmap. This patch enables TIME sample for per-cpu mmap and doesn't enable CPU sample. For later extension (e.g. support multiple AUX events), it sets the dummy event when the condition "opts->full_auxtrace" is true. Signed-off-by: Leo Yan <redacted> --- tools/perf/arch/arm64/util/arm-spe.c | 30 ++++++++++++++++------------ 1 file changed, 17 insertions(+), 13 deletions(-)diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c index 902e73a64184..f6eec0900604 100644 --- a/tools/perf/arch/arm64/util/arm-spe.c +++ b/tools/perf/arch/arm64/util/arm-spe.c@@ -70,7 +70,6 @@ static int arm_spe_recording_options(struct auxtrace_record *itr, struct evsel *evsel, *arm_spe_evsel = NULL; struct perf_cpu_map *cpus = evlist->core.cpus; bool privileged = perf_event_paranoid_check(-1); - struct evsel *tracking_evsel; int err; sper->evlist = evlist;@@ -126,18 +125,23 @@ static int arm_spe_recording_options(struct auxtrace_record *itr, evsel__set_sample_bit(arm_spe_evsel, CPU); /* Add dummy event to keep tracking */ - err = parse_events(evlist, "dummy:u", NULL); - if (err) - return err; - - tracking_evsel = evlist__last(evlist); - evlist__set_tracking_event(evlist, tracking_evsel); - - tracking_evsel->core.attr.freq = 0; - tracking_evsel->core.attr.sample_period = 1; - evsel__set_sample_bit(tracking_evsel, TIME); - evsel__set_sample_bit(tracking_evsel, CPU); - evsel__reset_sample_bit(tracking_evsel, BRANCH_STACK); + if (opts->full_auxtrace) { + struct evsel *tracking_evsel;
Hi Leo, I know the "if (opts->full_auxtrace)" pattern is copied from other auxtrace files, but I don't think it does anything because there is this at the top of the function: if (!opts->full_auxtrace) return 0; The same applies for other usages of "full_auxtrace" in the same function. They are all always true. I'm also not sure if it's ever defined what full_auxtrace means. James
+ + err = parse_events(evlist, "dummy:u", NULL); + if (err) + return err; + + tracking_evsel = evlist__last(evlist); + evlist__set_tracking_event(evlist, tracking_evsel); + + tracking_evsel->core.attr.freq = 0; + tracking_evsel->core.attr.sample_period = 1; + + /* In per-cpu case, always need the time of mmap events etc */ + if (!perf_cpu_map__empty(cpus)) + evsel__set_sample_bit(tracking_evsel, TIME); + } return 0; }