[3/3] trace-cruncher: Add example for the high-level synth. events APIs

Commit Message

Yordan Karadzhov Feb. 3, 2022, 3:35 p.m. UTC

This is a very basic example, demonstrating the usage of the new
high-level Python APIs for kernel synthetic events.

Signed-off-by: Yordan Karadzhov (VMware) <[e-mail]>
---
 examples/synth_oop.py | 45 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 examples/synth_oop.py

Patch

diff --git a/examples/synth_oop.py b/examples/synth_oop.py
new file mode 100644
index 0000000..865e784
--- /dev/null
+++ b/examples/synth_oop.py
@@ -0,0 +1,45 @@ 
+#!/usr/bin/env python3
+
+"""
+SPDX-License-Identifier: CC-BY-4.0
+
+Copyright 2021 VMware Inc, Yordan Karadzhov (VMware) <[e-mail]>
+"""
+
+import tracecruncher.ftracepy as ft
+import tracecruncher.ft_utils as tc
+
+# We will define a synthetic event, to be recorded every time a 'start' event is
+# followed by an 'end' event and both events have the same value of a 'match' field. 
+
+# Get the static kernel event 'sched_waking' and 'sched_switch' from system
+# 'sched'. Those two events will be used to create the synthetic event.
+swaking = tc.event('sched', 'sched_waking')
+sswitch = tc.event('sched', 'sched_switch')
+
+# Add to the synth. event two fields from the 'start' event (sched_waking). In the
+# synth. event, the field 'target_cpu' will be renamed to 'cpu'. Use the 'pid' field
+# for matching with the corresponding 'end' event.
+start = tc.ksynth_event_item(event=swaking, fields=['target_cpu', 'prio'], match='pid')
+start = tc.ksynth_field_rename(start, field='target_cpu', name='cpu')
+
+# Add to the synth. event one field from the 'end' event (sched_switch).
+# Use the 'next_pid' field for matching with the corresponding 'start' event.
+end = tc.ksynth_event_item(event=sswitch, fields=['prev_prio'], match='next_pid')
+
+# Define a synthetic event. The 'match' value will be recorder as a field in the
+# synth. event using 'pid' as name. We also add to the synth. event a field that
+# measures the time-difference between the 'start' and 'end' events. This new field
+# will use 'hd' time resolution (nanoseconds).
+synth = tc.ksynth(name='synth_wakeup', start_event=start, end_event=end,
+                  synth_fields=[tc.ksynth_field_deltaT(hd=True)], match_name='pid')
+
+# Create new instance of Ftrace.
+inst = ft.create_instance()
+
+# Apply a filter and enable the synth. event.
+synth.set_filter(instance=inst, filter='prio<100')
+synth.enable(instance=inst)
+
+# Print the stream of trace events. "Ctrl+c" to stop tracing.
+ft.read_trace(instance=inst)