tp: fix kernel idle tasks for boot-time traces
In boot-time traces, CPU scheduling tracks contain "swapper/0" tasks,
which should be hidden on the UI. These idle tasks show up because
kernel startup traces contain the following events:
event {
timestamp: 17000000
pid: 1
task_newtask {
pid: 0
comm: "swapper/0"
clone_flags: 256
oom_score_adj: 0
}
}
that /sbin/init creates more swapper/0 kernel idle tasks with pid/tid ==
0. Filter these task_newtask events since they do not create real new
threads.
Bug: 379009092
Change-Id: I556e085e35ca622fcfee7a3b5122f853eead05eadiff --git a/src/trace_processor/importers/ftrace/ftrace_parser.cc b/src/trace_processor/importers/ftrace/ftrace_parser.cc
index d9b130e..59b2446 100644
--- a/src/trace_processor/importers/ftrace/ftrace_parser.cc
+++ b/src/trace_processor/importers/ftrace/ftrace_parser.cc
@@ -2268,6 +2268,22 @@
// family) and thread creation (clone(CLONE_THREAD, ...)).
static const uint32_t kCloneThread = 0x00010000; // From kernel's sched.h.
+ if (PERFETTO_UNLIKELY(new_tid == 0)) {
+ // In the case of boot-time tracing (kernel is started with tracing
+ // enabled), the ftrace buffer will see /bin/init creating swapper/0 tasks:
+ // event {
+ // pid: 1
+ // task_newtask {
+ // pid: 0
+ // comm: "swapper/0"
+ // }
+ // }
+ // Skip these task_newtask events since they are kernel idle tasks.
+ PERFETTO_DCHECK(source_tid == 1);
+ PERFETTO_DCHECK(base::StartsWith(evt.comm().ToStdString(), "swapper"));
+ return;
+ }
+
// If the process is a fork, start a new process.
if ((clone_flags & kCloneThread) == 0) {
// This is a plain-old fork() or equivalent.
diff --git a/test/trace_processor/diff_tests/parser/parsing/tests.py b/test/trace_processor/diff_tests/parser/parsing/tests.py
index 54707c1..8af739d 100644
--- a/test/trace_processor/diff_tests/parser/parsing/tests.py
+++ b/test/trace_processor/diff_tests/parser/parsing/tests.py
@@ -1570,3 +1570,76 @@
5230422153284,0,1306,"[NULL]"
5230425693562,0,10,1
"""))
+
+ # Kernel idle tasks created by /sbin/init should be filtered.
+ def test_task_newtask_swapper_by_init(self):
+ return DiffTestBlueprint(
+ trace=TextProto(r"""
+ packet {
+ first_packet_on_sequence: true
+ ftrace_events {
+ cpu: 1
+ event {
+ timestamp: 1000000
+ pid: 0
+ task_newtask {
+ pid: 1
+ comm: "swapper/0"
+ clone_flags: 8389376
+ oom_score_adj: 0
+ }
+ }
+ event {
+ timestamp: 1000000
+ pid: 0
+ task_newtask {
+ pid: 2
+ comm: "swapper/0"
+ clone_flags: 8390400
+ oom_score_adj: 0
+ }
+ }
+ event {
+ timestamp: 17000000
+ pid: 1
+ task_newtask {
+ pid: 0
+ comm: "swapper/0"
+ clone_flags: 256
+ oom_score_adj: 0
+ }
+ }
+ event {
+ timestamp: 17000000
+ pid: 1
+ task_newtask {
+ pid: 0
+ comm: "swapper/0"
+ clone_flags: 256
+ oom_score_adj: 0
+ }
+ }
+ event {
+ timestamp: 17000000
+ pid: 1
+ task_newtask {
+ pid: 0
+ comm: "swapper/0"
+ clone_flags: 256
+ oom_score_adj: 0
+ }
+ }
+ }
+ trusted_uid: 9999
+ trusted_packet_sequence_id: 2
+ trusted_pid: 521
+ previous_packet_dropped: true
+ }
+ """),
+ query="""
+ SELECT utid, tid, name from thread where tid = 0
+ """,
+ out=Csv("""
+ "utid","tid","name"
+ 0,0,"swapper"
+ """))
