Rename db_export__comm() to db_export__exec_comm() to better reflect what it does and add explanatory comments.
Signed-off-by: Adrian Hunter <[email protected]> --- tools/perf/util/db-export.c | 22 +++++++++++++++++++--- tools/perf/util/db-export.h | 4 ++-- 2 files changed, 21 insertions(+), 5 deletions(-) diff --git a/tools/perf/util/db-export.c b/tools/perf/util/db-export.c index f36970018df3..bb696559cd9a 100644 --- a/tools/perf/util/db-export.c +++ b/tools/perf/util/db-export.c @@ -104,8 +104,14 @@ int db_export__thread(struct db_export *dbe, struct thread *thread, return err; } -int db_export__comm(struct db_export *dbe, struct comm *comm, - struct thread *main_thread) +/* + * Export the "exec" comm. The "exec" comm is the program / application command + * name at the time it first executes. It is used to group threads for the same + * program. Note that the main thread pid (or thread group id tgid) cannot be + * used because it does not change when a new program is exec'ed. + */ +int db_export__exec_comm(struct db_export *dbe, struct comm *comm, + struct thread *main_thread) { int err; @@ -120,6 +126,16 @@ int db_export__comm(struct db_export *dbe, struct comm *comm, return err; } + /* + * Record the main thread for this comm. Note that the main thread can + * have many "exec" comms because there will be a new one every time it + * exec's. An "exec" comm however will only ever have 1 main thread. + * That is different to any other threads for that same program because + * exec() will effectively kill them, so the relationship between the + * "exec" comm and non-main threads is 1-to-1. That is why + * db_export__comm_thread() is called here for the main thread, but it + * is called for non-main threads when they are exported. + */ return db_export__comm_thread(dbe, comm, main_thread); } @@ -312,7 +328,7 @@ int db_export__sample(struct db_export *dbe, union perf_event *event, goto out_put; if (comm) { - err = db_export__comm(dbe, comm, main_thread); + err = db_export__exec_comm(dbe, comm, main_thread); if (err) goto out_put; es.comm_db_id = comm->db_id; diff --git a/tools/perf/util/db-export.h b/tools/perf/util/db-export.h index 261cfece8dee..148a657b1887 100644 --- a/tools/perf/util/db-export.h +++ b/tools/perf/util/db-export.h @@ -76,8 +76,8 @@ int db_export__evsel(struct db_export *dbe, struct perf_evsel *evsel); int db_export__machine(struct db_export *dbe, struct machine *machine); int db_export__thread(struct db_export *dbe, struct thread *thread, struct machine *machine, struct comm *comm); -int db_export__comm(struct db_export *dbe, struct comm *comm, - struct thread *main_thread); +int db_export__exec_comm(struct db_export *dbe, struct comm *comm, + struct thread *main_thread); int db_export__comm_thread(struct db_export *dbe, struct comm *comm, struct thread *thread); int db_export__dso(struct db_export *dbe, struct dso *dso, -- 2.17.1
