[PATCH 09/10] trace-cruncher: Add synthetic event example

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

This is a very basic example, demonsting the usage of the new APIs
for kernel synth. events.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 examples/synth.py | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100755 examples/synth.py

diff --git a/examples/synth.py b/examples/synth.py
new file mode 100755
index 0000000..ec9427b
--- /dev/null
+++ b/examples/synth.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+
+"""
+SPDX-License-Identifier: CC-BY-4.0
+
+Copyright 2021 VMware Inc, Yordan Karadzhov (VMware) <y.karadz@gmail.com>
+"""
+
+import tracecruncher.ftracepy as ft
+
+# Define a synthetic event that combines 'sched_waking' and 'sched_switch'.
+# A synth. event will be recorded every time a 'start' event (sched_waking)
+# is followed by an 'end' event (sched_switch) and both events have the same
+# value of the fields 'pid' and 'next_pid' (belong to the same process).
+synth = ft.synth(name='synth_wakeup',
+                 start_sys='sched', start_evt='sched_waking',
+                 end_sys='sched',   end_evt='sched_switch',
+                 start_match='pid', end_match='next_pid',
+                 match_name='pid')
+
+# Add to the synth. event two fields from the 'start' event. In the synth. event,
+# the field 'target_cpu' will be renamed to 'cpu'.
+synth.add_start_fields(fields=['target_cpu', 'prio'],
+                       names=['cpu', None])
+
+# Add to the synth. event one field from the 'end' event.
+synth.add_end_fields(fields=['next_prio'])
+
+# Add to the synth. event a field that measures the time-difference between
+# the 'start' and 'end' events. Use 'hd' time resolution (nanoseconds).
+synth.add_delta_T(hd=True)
+
+# Register the synth. event on the system.
+synth.register()
+
+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)
-- 
2.32.0