diff options
| -rw-r--r-- | tools/perf/Documentation/perf-record.txt | 3 | ||||
| -rw-r--r-- | tools/perf/builtin-record.c | 30 |
2 files changed, 32 insertions, 1 deletions
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index d5217be012d79..1889f66addf2a 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -374,6 +374,9 @@ comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0- In per-thread mode with inheritance mode on (default), samples are captured only when the thread executes on the designated CPUs. Default is to monitor all CPUs. +User space tasks can migrate between CPUs, so when tracing selected CPUs, +a dummy event is created to track sideband for all CPUs. + -B:: --no-buildid:: Do not save the build ids of binaries in the perf.data files. This skips diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 83bd1f117191e..dcf288a4fb9a9 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -906,10 +906,30 @@ static int record__config_off_cpu(struct record *rec) return off_cpu_prepare(rec->evlist, &rec->opts.target, &rec->opts); } +static bool record__tracking_system_wide(struct record *rec) +{ + struct evlist *evlist = rec->evlist; + struct evsel *evsel; + + /* + * If non-dummy evsel exists, system_wide sideband is need to + * help parse sample information. + * For example, PERF_EVENT_MMAP event to help parse symbol, + * and PERF_EVENT_COMM event to help parse task executable name. + */ + evlist__for_each_entry(evlist, evsel) { + if (!evsel__is_dummy_event(evsel)) + return true; + } + + return false; +} + static int record__config_tracking_events(struct record *rec) { struct record_opts *opts = &rec->opts; struct evlist *evlist = rec->evlist; + bool system_wide = false; struct evsel *evsel; /* @@ -919,7 +939,15 @@ static int record__config_tracking_events(struct record *rec) */ if (opts->target.initial_delay || target__has_cpu(&opts->target) || perf_pmus__num_core_pmus() > 1) { - evsel = evlist__findnew_tracking_event(evlist, false); + + /* + * User space tasks can migrate between CPUs, so when tracing + * selected CPUs, sideband for all CPUs is still needed. + */ + if (!!opts->target.cpu_list && record__tracking_system_wide(rec)) + system_wide = true; + + evsel = evlist__findnew_tracking_event(evlist, system_wide); if (!evsel) return -ENOMEM; |