Hi, I found that the timestamps from babeltrace and python binding are different in nanoseconds level.
skim@d54030999178:~/ssd_work/traces$ python3 test.py ./trace/ | head -n 10 2019-12-12 13:45:40.098212096 (+0.000000 s): syscall_exit_ppoll 2019-12-12 13:45:40.098213608 (+0.000001 s): rcu_utilization 2019-12-12 13:45:40.098214632 (+0.000001 s): syscall_entry_ioctl 2019-12-12 13:45:40.098214888 (+0.000000 s): kmem_kfree 2019-12-12 13:45:40.098214144 (+0.000000 s): rcu_utilization 2019-12-12 13:45:40.098215168 (+0.000001 s): sched_stat_runtime 2019-12-12 13:45:40.098220776 (+0.000004 s): sched_switch 2019-12-12 13:45:40.098221312 (+0.000002 s): timer_hrtimer_cancel 2019-12-12 13:45:40.098221312 (+0.000000 s): kmem_kmalloc 2019-12-12 13:45:40.098223360 (+0.000002 s): kmem_kfree Traceback (most recent call last): File "test.py", line 33, in <module> print(fmt.format(dt, ns_from_origin % 1e3, diff_s, msg.event.name)) BrokenPipeError: [Errno 32] Broken pipe skim@d54030999178:~/ssd_work/traces$ babeltrace2 ./trace/ | head -n 10 [13:45:40.098211969] (+?.?????????) test-sys syscall_exit_ppoll: { cpu_id = 3 }, { ret = 0, nfds = 1, fds_length = 0, overflow = 0, fds =[ ] } [13:45:40.098212481] (+0.000000512) test-sys rcu_utilization: { cpu_id = 5 }, { s = "Start context switch" } [13:45:40.098213729] (+0.000001248) test-sys syscall_entry_ioctl: { cpu_id = 2 }, { fd = 24, cmd = 1075331408, arg = 547894601712 } [13:45:40.098213953] (+0.000000224) test-sys kmem_kfree: { cpu_id = 3 }, { call_site = 0xFFFFFF800153B274, ptr = 0x0 } [13:45:40.098214017] (+0.000000064) test-sys rcu_utilization: { cpu_id = 5 }, { s = "End context switch" } [13:45:40.098215201] (+0.000001184) test-sys sched_stat_runtime: { cpu_id = 5 }, { comm = "Positioning", tid = 1056, runtime = 38048, vruntime = 2125241692 } [13:45:40.098219681] (+0.000004480) test-sys sched_switch: { cpu_id = 5 }, { prev_comm = "Positioning", prev_tid = 1056, prev_prio = 15, prev_state = 1, next_comm = "Sensor", next_tid = 1061, next_prio = 15 } [13:45:40.098221313] (+0.000001632) test-sys timer_hrtimer_cancel: { cpu_id = 5 }, { hrtimer = 0xFFFFFFC257807CD8 } [13:45:40.098221409] (+0.000000096) test-sys kmem_kmalloc: { cpu_id = 0 }, { call_site = 0xFFFFFF80014A27EC, ptr = 0xFFFFFFC04EDFA400, bytes_req = 739, bytes_alloc = 1024, gfp_flags = 37748928 } [13:45:40.098223361] (+0.000001952) test-sys kmem_kfree: { cpu_id = 5 }, { call_site = 0xFFFFFF8008164C58, ptr = 0x0 } The difference is not consistent and Trace Compass shows the same timestamp with the babeltrace output, so I think something is wrong in my python code. I just modified the example script from https://babeltrace.org/docs/v2.0/python/bt2/examples.html#get-an-event-s-time to show nanoseconds as below. diff: 32,33c32,33 < fmt = '{} (+{:.6f} s): {}' < print(fmt.format(dt, diff_s, msg.event.name)) --- > fmt = '{}{:03.0f} (+{:.6f} s): {}' > print(fmt.format(dt, ns_from_origin % 1e3, diff_s, msg.event.name)) Full code: import bt2 import sys import datetime # Create a trace collection message iterator from the first command-line # argument. msg_it = bt2.TraceCollectionMessageIterator(sys.argv[1]) # Last event's time (ns from origin). last_event_ns_from_origin = None # Iterate the trace messages. for msg in msg_it: # `bt2._EventMessageConst` is the Python type of an event message. if type(msg) is bt2._EventMessageConst: # Get event message's default clock snapshot's ns from origin # value. ns_from_origin = msg.default_clock_snapshot.ns_from_origin # Compute the time difference since the last event message. diff_s = 0 if last_event_ns_from_origin is not None: diff_s = (ns_from_origin - last_event_ns_from_origin) / 1e9 # Create a `datetime.datetime` object from `ns_from_origin` for # presentation. Note that such an object is less accurate than # `ns_from_origin` as it holds microseconds, not nanoseconds. dt = datetime.datetime.fromtimestamp(ns_from_origin / 1e9) # Print line. fmt = '{}{:03.0f} (+{:.6f} s): {}' print(fmt.format(dt, ns_from_origin % 1e3, diff_s, msg.event.name)) # Update last event's time. last_event_ns_from_origin = ns_from_origin Could someone help what was wrong in the python code? Or is this a bug in ns_from_origin implementation? I'm using below version. skim@d54030999178:~/work/tmp$ babeltrace2 -V Babeltrace 2.0.4 "Amqui" Amqui (/_mkwi_/) is a town in eastern Qu_bec, Canada, at the base of the Gasp_ peninsula in Bas-Saint-Laurent. Located at the confluence of the Humqui and Matap_dia Rivers, its proximity to woodlands makes it a great destination for outdoor activities such as camping, hiking, and mountain biking. skim@d54030999178:~/work/tmp$ apt list python3-bt2 Listing... Done python3-bt2/bionic,now 2.0.x+stable+git4134+202007172102~ubuntu18.04.1 amd64 [installed] Best regards, Seongab Kim _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev